If you're going to ride a lot then it's worth while spending a bit of money. At the end of the day it's the frame you'll be interested in as all other bits and pieces can be retrofitted to improve the ride.
As far as handlebars are concerned, it's a matter of comfort. if you're tall and on a mid sized frame then riser bars will be required or you'll be like me, with comfort problems. Risers are normally wider and give more control.
Get a good quality hard tail which you can upgrade and learn on. You could later upgrade to a full bouncer frame using all the upgraded hardware. I bought a hardtail and have no regrets about it. I'm looking at upgrading to a full bouncer but at the moment I'mm having too much fun!
Brakes and forks will come on a parr with the quality bike (do some investigation on the equipment). Hydraulic disc brakes are well worth while if you're XC' in mucky stuff. Quality Mech disc brakes are just as good and the latest ones are similar to Hyd's.
Forks, well I think you need to ride the bike 150Km or so to find out wether they're good or bad so do investigation on these as well. Read mags or search the net and get some feedback.
At the end of the day, what ever bike you get, just get out and ride!!