My discord is @childof_light

friend me, and I will help you

Forget about upgrading all the gray mechs except maybe Lancer, if you like that kind of action. Paragon is ok, but I'd still move on. 

Guardian and Tengu will last a long time and worth upgrading.

Normally when I'm figuring out builds, first thing to look at is spd, hp and ability stats of the mech in question. 

Let's say redeemer. It's hp isn't too high, speed is quite decent so stuff that are hit and run is good for it. Ability pairs even better up with hit and run. So from there, we can conclude that redeemer does best with barrage and missile weapons. Which is true in game.

You could also ask ppl in chat or review player's hangers and see what they currently use.