My suggestions----Clay bar your truck first---it gives you a clean "foundation" to work with. I would recommend that after you clay bar it, check for any small scratches that the clay might have caused and if so use a good polish to polish them out. I would then use a good sealant as a base coat. The sealant can be topped with a good wax of your choice. It sounds a little time comsuming and it is the first time, but the results are well worth it. Once you have a good base you can maintain it by just washing your truck and then using a quick detailer on it inbetween waxes. A good sealant will last you about 6 months and wax will only last about 4-6 weeks. That is the reason I recommend using a good sealant first--you will have longer protection. Asking which wax or sealant is best is like asking what beer people like best----everyone has their favorite that is the best, cheapest, easiest, longest lasting, smells the best etc et etc., you get the idea. I use Wolfgang 3.0 Sealant and Collinite 845 Wax but there are many other people that use many other products. Always use good microfiber to reduce the chances of getting small scratches.
Good luck
Jay