In general, shooting matches is not expensive. like others told you above, you only shoot few rounds and pay $10-$20 fee.
Lot cheaper than drinking beer

What is expensive, is training for good scores and/or moving up to high classifications. With proper training, you can move up from low classifications pretty fast. I could tell some stories about my wife, but maybe she can tell it by herself.

Any gun will do, but... If you really want to develop your skills, you need an easy gun to shoot, specially in the beginning - something pretty heavy weight, decent sights, good trigger etc.
GM´s can shoot many guns fast and accurately. They know from experience, how to use advantages and disadvantages of a gun, for example Glock - how to deal with long trigger reset, heavy, long and not very accurate trigger pull etc. For beginner, this is lot harder.

Dry firing is cheap and it will go a long way. Dry fire 2 times a day and you can see improvement pretty fast.

When you shoot matches, _never_ try to push yourself fast. Speed comes with practice, if you try to force it you only develop bad ways of doing to your subconscious mind.
_Never_ think like : "I would be a real badass, but I can not do well because of my eqiupment". I could tell some experiences, but maybe later