Lets face it dirtbikes are't cheap but you can still get the dirtbike experience for just a fraction of the price then the average dirtbike rider.
The most expensive peace of gear happens to be the most important the Dirtbike.
Surching for the right Dirtbike is a roller coaster ride full of temptation bargaining and wishing you had a better budget. since you are on a budget it only makes sence to buy a second hand bike rather then a brand new one I highly recommend trade me for this. By far the most important thing to do is stay patient. Check if any new bikes have been listed at least twice a day to get a jump on those deals were the bike gets sold in a mater of hours. dont get exited by a deal and rush head first into it stay sceptical and dont forget to ask questions concerning the state of the bike.