Our first RV was a new 1994 20' TT and I had a 1993 Chevy Astro Van. The van was capable of towing this little trailer, but it didn't have the suspension when we were full of water and supplies and it once nearly got us in a wreck. I then got a '96 GMC Jimmy with better towing results, but my '99 Ford F150 handled it best.
Then, after discovering this website in '02, I decided a 5th wheel was the way to go so I purchased the truck first, an '02 Chevy Duramax Diesel (still have it). Found a perfect small used '01 Cardinal 5ver (still have that too). Could be happier with both, even after all these years. If fact, after looking for a newer 5ver this year, and not being able to find what I wanted, decided to keep my '01 Cardinal because it was in excellent shape and we tow to Florida for the winter and take it out often in the summer.
Bottom line: Really decide what kind of RV you want first. A good recently used camper is a good idea because of the savings you will realize over purchasing new. But if you really want new that's up to you. Just remember that many RV owners usually enjoy their first RV and almost always want something a "little bit" bigger, especially if they enjoy camping and/or taking lengthy trips. Diesels, especially new ones, are expensive. If you want to pull a toy hauler or a nice sized 5ver you'll do best with a diesel because gassers, pulling that kind of weight, get very poor mileage. If you think you'll be happy with a TT in the 22'-27' range a gasser with a good towing suspension may work for you, but the mileage will still be poor.