Full disclosure is I have never had an F150, but I have had several F250's as well as Jeeps, Chevys, Dodges, etc.
Here is my two cents on any rig: what you care about is traction, clearance, angles (approach departure and break over), articulation, gears and durability.
F150 is a perfectly fine platform to start with and I dont get why people would say it isnt. Easy to get a tad more lift, lose the air dams, check the rear to see if angles can be improved out back, figure out what gears you have, figure out what tires you can take, and go from there.
I am guessing you can do quite a lot without spending a tremendous amount of money.
The thread on my F250 build
http://www.expeditionportal.com/forum/showthread.php?t=54302
can do a lot with out spending a lot