Few tips for #tryhard :
don't buy a new mech if you can't have a full loadout of internals and items. Start with classic 2x EMP / 2x shields, deflectors / air compressor + 1slot and adjust after depending on your playstyle.
play a few coop TDM when you try mechs for the first time.
when you buy a new mech, try to stick with it and level it up to max level (~20~30 hours)
check-out your accuracy stats and try to increase it. If needed buy multiple times the same mech to check if you progress or not.
type "stupid bots" in chat in coop TDM to increase the AI accuracy, can be usefull for practice.
learn not to yolo dive, to take cover after shooting with your secondary, to lead your shot with projectile weapons (don't shoot grenades where people are, but where they will be).
You may use different reticules for the different weapons. try multiple reticules and find one that helps you with aiming.
Some mechs have primary weapons that are hard to use (rev-GL, BBY, mini-flak scout is harder to use than flak scout), be patient until you unlock the one you want and/or be prepared for hard time until you can use them efficiently
Don't push too hard your practice : some Mechs are just not good in all maps. for example play burst mechs in wreckage and avoid them in bunker / bazaar, in the same way avoid reaper in wreckage...
Don't try playing EOC repeater unless you wanna have fun with a crappy weapon (breacher pred, seeker rocketeer).
Also you should avoid the "cheese" : avoid playing salt too much, avoid rocketeer / sharpshooter in bunker, avoid teching an incin', avoid orblording.
Learn to play tech but for the sole purpose of playing tech if the other team has one and not your team.
Learn to play PPA incin' but for the sole purpose of being deaf and speedrunning coop bot destruction.