Hey Alex, to add to what Petko has said.
How much you trade depends on your risk tolerance you want to make sure that first you are at no risk of a margin call so should calculate what your max margin would be if you had an open trade on all your EAs and adjust accordingly (use half your margin at most).
Also you should have rough idea of what your range of profit/drawdown would be per month or so, best to make sure that also this limits your drawdown to your risk tolerance. 5% a month works for my sanity