1. Something like MAG brand midcaps would work well.
2. You would need to get triple deep M4 pouches, or pouches specifically made to fit 2x G36 mags.
3. A good MOLLE covered vest. Don't buy a crappy one with holster and random pouches that you can't change. Buy a modular vest and moldular pouches and you can set it up how you want. Buy a good brand like FLYYE or Pantac and it will last forever.
The vest will could cost you $80-$100 alone, so you better raise your budget.
You probably also want a dump pouch of some sort.
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