My first attempt at a build guide.  I will preface, I am not a min/max player (nothing wrong with those who are), so I will not call the gear/items I use as BiS.  However, I will explain the best I can why I chose the gear/talents/IP/synergies for my build.  Without further ado;

TALENTS

Talent Row 1: Run Through- This talent triggers a 'free'  every 4s as long as 500 debris or more is collected.  With the artifact choices (explanation later), Mags will be above 500 debris for nearly 100% uptime. This talent is practically mandatory for all Magneto builds (the only real BiS anything I will say for Mags).

Talent Row 2: Super Compression (build recommended)- I chose this talent because it gives  (big hitter power) 100% critical chance, a 25% damage increase, & a -50% Debris cost and gives  (spender) 100% critical chance, a 25% damage increase, and a -50% debris cost.  This talent ends up giving  (including Run Through talent Impale) and  only critical/brutal hits.

Talent Row 3: Waste Not (build recommended)- This talent increases all debris spending powers by 15% and increases debris collected from debris orbs by 10.  This talent increases the damage of all of powers used with exception of  & .

Talent Row 4: God Among Insects (build recommended)- This talent reduces the cooldown of  by 15 seconds.  Mags has one of the best Signatures, imho, so why not reduce the cooldown to be able to use it more often.

Talent Row 5: Polarity Shift (build recommended)- This talent adds a positive polarity to  increasing damage to debris generator powers by 30% for 6s and a negative polarity to  increasing damage to debris spending powers by 30% for 6s.  I use  for knocking enemies into the air (including bosses) and the additional 30% damage to all debris spending powers.  **Note: I know on this website the tooltip says both polarities increase debris generator powers, however in game negative polarity actually increases debris spending powers.**

GEAR

Slot 1:  (build recommended)- good damage with some needed defensive utilities. Adds critical damage & brutal damage rating on Critical Hit.  is a good placeholder until Frag is crafted/looted.

Slot 2:  (build recommended)- There are very little options for Mags for slot 2.  I found a Cosmic slot 2 with Critical Hit Rating, Critical Damage rating, and Brutal Damage rating.  is a decent placeholder until the recommended cosmic slot 2 is found.

Slot 3:  (build recommended)- A LOT of awesome offensive stats, including pretty good increases to brutal strike & brutal damage ratings.  Also increases damage rating, INT & ENG on critical hit.   is a good placeholder until Coat is looted.

Slot 4-  (build recommended)- The brutal strike and brutal damage ratings are too good here.  This also comes with some health, and a damage rating & INT attribute increase on critical hit.   is a good placeholder until Skrull Uniform is looted.

Slot 5-  (build recommended)- Another unique with a lot of great offensive stats for Mags, including a proc that can increase ENG attribute stat up to a +9 (depnding on roll of course).  is a good placeholder until Jinn is crafted/looted.

Legendary:  (build recommended) both lvl 70/80 as the build stacks critical hit/critical damage rating & brutal strike/brutal damage rating.  Other options: , 

Catalyst: Current catalyst affixes *Build recommended affixes in bold*

• +3 INT
• 25% health/+100 debris on Medkit use
• defense
• %XP
• Armored catalyst (1,000 defense)
• Crafted affixes- all critical damage 90% or higher
• Cosmic affix- gain a shield equal to 50% max health on Medkit use
• Mutant bonus- gain 1,000 health per sec for 10s below 40% health (whatever comes with the recommended affixes)

Ring: The current offensive ring I use stacks critical damage & brutal damage rating.   is a great placeholder.  is a decent placeholder until Sling Ring or crit/brut damage ring looted.

Relic:  stacking critical damage.   is a decent placeholder.   if feeling too squishy.

Uru:  &  adding defense where possible. Power Doop stacks more critical damage on energy power hit and +17 debris each Doop proc on a 7s cooldown.  is a suitable replacement instead of running Power Doop.   is a decent placeholder until Doop rune is looted or the elusive Tyr rune is looted for Bowazon.  Other Uru options: , 

Insignia:  or  are both great and work for Mags.  I am currently using Storm because I looted one with critical damage & brutal damage rating.

Medallion:  cosmic version (build recommended).  Adds INT attribute (up to 4 INT with proc active) with ranged and area damage increase.   is a good placeholder until non-cosmic/cosmic Infernal War Skrull medallion is looted.

Pet:

• Green: 5% Total Defense Rating (current).  %Base Health works too.
• Blue: +50 debris
• Purple: 10% brutal damage rating
• Yellow: Gain 4% brutal damage rating & 4% attack speed on hit. (website says 4% critical damage, however in game it is brutal damage)
• Unique: +3 Intelligence

Team- Up:  she is a good tank, can pull enemies towards her, applies weaken, and she can even trigger the auto  talent while attacking (any team-up attacking can trigger it).  Other options: , , , , , 

ROTATION

 

Rotation is relatively simple overall.

Hold ,  to apply Vulnerability and a 8s DoT,  to apply another 8s DoT,  for knock in the air and debris spender damage increase for 6s,  immediately after to take advantage of the 30% increased damage buff.  Refresh DoTs, use  &  off cooldown.  Use  as needed for debris orbs and some extra damage.  Use  on bosses or giant packs of enemies.  During the rotation Run Through talent will be going off every 4s for the 'free'  while above 500 debris.

ARTIFACTS

Build recommended artifacts: all cosmic versions. Non-cosmic versions work until cosmic versions are looted/bought (Cyc Shirt is bought with Danger Room merits).  

 for Critical Hit, Critical Damage, Brutal Strike, & Brutal Damage ratings increase.

 for INT attribute increase, damage rating increase, Critical Hit & Brutal Strike rating increase.

 for ENG attribute increase, debris increase, debris cost reduction, defense increase, and a pretty good critical damage rating increase.  The main reason I chose this artifact is for when a critical hit occurs, Mags gains +3 debris on hit for 8s. Due to  &  being 100% crital hit rating, this is practiaclly a perma +3 debris on hit.

 for the INT & ENG attribute increase, Area Damage increase (all but 2 powers used are tagged area damage), increase Boss damage.  As with the previous artifact, this one was chosen because of the recover 4 debris on hit.

With  &  combined that is +7 debris (plus the +17 debris on energy power hit Power Doop proc every 7s) generated on every hit (1s interal cooldown).  Running the rotation, it is very rare Mags gets below 500 debris.  My Mags is currently sitting at 1100-ish debris and very rarely gets below 700 debris, especially if  is used regularly during rotation.  Debris orbs will be all over the place.

Other options: , , , , , , , , , 

Cosmic Artifact affixes:

• +1 all attributes in combat
• 10% cooldown reduction on Signature in combat (27s cooldown combined with God Among Insects talent)
• 15% debris cost reduction for all abilites in combat
• +1500 defense in combat

Blessings: x4 (stacking more brutal strike & brutal damage)

INFINITY POINTS

Build recommendation IP order:

1. +6 Intelligence Attribute (Mind Gem)

2. 150/150 Mental Focus (% Critical Damage rating, Mind Gem)

3. 75/75 Strike Through (% Brutal Damage rating, Power Gem)

4. 200/200 Patency (% Signature Base Damage, Reality Gem)

5. +6 Energy Attribute (Reality Gem)

6. 38/50 Temproal Loophole (Attack/Move Speed, Time Gem)

7. 150/150 Micro-Warps (% Base Total Defense Rating, Space Gem, current) or 50/150 Micro-Warps & 50/250 Gravity Well (% Base Health)

8. 25/50 Inner Relisience (Health on Hit, Soul Gem)

9. IP dump into Inelligence Attribute (build recommended) or where you see fit to place IPs.

SYNERGIES

Synergies are more flexible than the rest of the itemization.  *= the main synergies nearly all heroes use, the rest can be preference, except for the Archetype attribute damage bonus synergies (INT & ENG for Mags).

Currently used synergies:

• Beast (3% melee damage, +1 Intelligence)
• Black Bolt (3% Move Speed, 2% Critical Hit rating multiplier)
• *Cable (4% Critical Hit rating multiplier)
• *Doctor Doom (10% Signature damage increase)
• Gambit (+5 Credits per drop, +1 Energy)
• Hawkeye (2% Move Speed, 3% Critical Damage)
• Mr. Fantastic (5% Crafting Discount, 3% Critical Damage)
• *Squirrel Girl (4% Boss Damage)
• Ultron (3% Summon Power Damage, +1 Intelligence)
• *Wolverine (5% Brutal Strike rating multipler & 5% Brutal Damage)

That is it.  This guide does well in all content and I hope this helps any new Mags players get started.  I don't have TTK/TTL times and I am too tech illiterate to post videos of my build.  Any questions please ask.  Thanks for reading!