Unrecognized events aren't that expensive. Usually around the $100 - $150 mark for entry fee's.
You can do Dressage, Stadium and CC in the same saddle - I see people doing dressage in their cc, not a biggie.
Of course, tack is always expensive - but if you buy quallity used, you should be fine. I buy used all the time, and you can find great deals on www.tacktrader.com
and tack sales.
When you get to Recognized USEA events, that's when they get expensive. For example, I am planning on doing Richland Park this year, which is a 3 star rated course - and Novice alone is over $300.00 for their entry fee.
Unrecognized events, or local events - like T.E.A.M in my area, are very reasonably priced.
Anything to do with horses, is expensive.