My nostalgic appreciation of Mech Warrior/Commander made me interested in this game. Seems like more fun than it is -- it's not too fun to play. It's not much of a challenge either, at least, so it's not frustrating. Of the Con-Artists games, this is the one that featured the worst buyer's remorse -- a fair bit of the goods are plain mediocre. At least you can sell them back for some of the cost. You can get enough money to just about try everything, to be fair.
If you want the walkthrough hints: I found the shotgun cannon thing to be the best versus prisoners and the grenade launcher the best for mechs, as well as the second best for prisoners. Flamer is third best for them if only because it's so short ranged and makes you faff about the arena all the harder. Rockets were crap. Mines hurt, but aren't efficient when enemies spawn from 4 different zones randomly and frequently. Laser is too slow and precise. Didn't try the EMP gun. The rocket volley seemed forgettable, though maybe equipping 4 of them is fun. Same goes for the chainguns. I did equip 4 of the starting guns for the final boss -- didn't seem very good for it, but I beat him.
Heat sinks seemed more useful to equip than the other gear items, even when ignoring the prices. Upgrades are worthwhile, as you'd expect. Movement upgrade least of all, perhaps.
My gripe with the game is the movement. Even with the upgrades, it feels very sluggish and opposite of agile. You can pick up some speed, but it's a relatively small arena every time, foes spawning from all directions constantly, you gotta faff around it nonstop to avoid the flak and it's a bit too slow to turn and accelerating is also rather slow. I get that it's a mech, but given the style of gameplay, it's not enjoyable for it to feel so cumbersome. A more agile mech and tougher and/or more foes to balance it out might've been called for.
Boss hint: strafe the middle of the arena to avoid his shit and gun him down as he stays parked.
Overall hint: do go for the grenade launchers. They spread around and got some AOE, meaning you don't have to aim well, which isn't easy or fun to do in this game.