don't use 6 weapons, only use the ones you will will actually use in battle
upgrade and add modules, in this game survivability is key, the more turns you're able to survive the more turns you will be able to attack your enemy
however sick your mech may look now, don't waste tokens on painting your mech, tokens are necessary for getting the best items in the game
try to have all your weapons be the same type, mixing different types of weapons spreads your damage too thin, while concentrating on one doesn't
try to focus on upgrading items that can reach mythical level, they are the ones with epic, yellow, orange, and white circles next to their names
focus on upgrading your torso, legs, modules, weapons, in that order
while still keeping the last tip in mind, try upgrading all your items somewhat equally