I remember it taking a while to get used to the movement/combat system. For ranged combat, whenever possible set yourself up to be able to walk backwards while firing, that made a world of difference. (Dash/minus key to move in reverse). And I always wore a shield, usually one of the smaller/lighter ones because of the dang weight limits. I don't remember if it needed a skill for full effectiveness - for mechs maybe mech fighting? And close combat for personal? The big advantage was the chance to block one or more incoming attacks, made a huge difference. I remember starting out as "naked boomerang boy" (combat xp gained is reduced by the cost of your gear, so to max that out I'd go as cheap as possible, scouring the stores for the cheapest viable armor and weapons for each step up. Without huge initial spending on personal combat skills it was possible to outmaneuver low level stuff like rats, even coming from different directions.
For mech combat, make sure to keep moving! The penalty for them to hit greatly outweighs the penalty to your attacks. I used to know the ins and outs of the MV/TR modifiers, early on when your skill is low those make a HUGE difference. In gh1 it was possible to really cheese it, and load up on engines to give yourself ludicrous speed (and corresponding defensive bonuses).
Damn, it's making me want to fire it up again. Oh, if you're doing it ascii, definitely adjust the rows/columns to give yourself a bigger view, made a huge improvement in navigation and situational awareness.