I'd look for a truck/camper combination already set up ... Craigslist or on the RV sales sites. Otherwise, you need to consider 'extras' like the tie-downs and electrical connectors in the truck bed. It all adds up if you're on a budget.
Failing that -- I'd start looking for a truck and a camper you like, and see what each one costs, try to balance camper needs against a dependable truck. Camper does you little good sitting on a site with no truck to move it.
I agree with priority buying good solid camper. It's easier to upgrade a truck than a camper - campers lose value quickly. So finding a good one and maintaining it is a good idea.
I can't tell what kind of prices go for trucks that would satisfy you - used 250/2500 (stay away from 150/1500) trucks new enough to be dependable hold value pretty well. Even tho you want a "good camper" -- you'll probably spend a larger proportion of your budget on a truck ... it's just the market.
Once you start, don't settle. Find what you want once, because you can't afford to make a mistake and buy twice. But if you take your time, you will find a combination you like and suits your spending.
