For $3500 you should be able to get a good used boat rigged and ready to go. A new boat, fully rigged, should run you more. If you are mainly fishing mellow, riffled trout streams fiberglass, or aluminum will do nicely for you. If you are going to float fast, heavy water, with large rocks (like many of our coastal rivers are) I would advise you to go aluminum. Note: when buying a used aluminum boat look at the under-side beneath the front bench seats to check for the floor being indented between the floor runners.
Also, given your size, I would recommend a 16' boat with a 54" bottom width. The added surface area will make it row easier for you.