couple of tips
1) pick 9 or 10 dudes and their mechs you like and upgrade the shit out of them, also know what each mech is good at and taking full advantage of that helps. like grungust, dont waste points on mobility with them since they are slow anyway, maximize their armor so that enemies wont do much damage to them.
2) when upgrading weapons, pick the one you use the most with that mech and upgrade the crap out of it. try to also upgrade their best move a bit, since it helps against boss fights a lot. you can also upgrade a couple of machine guns since almost every mech can use those and they are cheap to upgrade.
3) when it comes to giving points to a pilot, try to give him/her skills that benefit what they are good at. for example Excellen is good a longe range attacks so giving her skills/abilities that help with her style would be a good idea.