Befriend a boatbuilder....someone who knows way more than you do.

Buy the best power tools you can afford...even if they are out of your price range.

Keep building materials handy.  Have on hand what you need to make repairs without having to stop everything to go to the hardware store for a board. 

Buy those inexpensive paint brushes and get good use out of them.  After a few days of use and cleaning, throw them away.

NEVER get too attached to a piece of rope.  Replace  mooring lines, anchor lines, the bow line (called the Tew), the life line, and any other rope associated with your boat often.  Dryrotted rope is a disaster just waiting to happen.

You're better off buying 4 one quart cans of paint over a one gallon can.  Used only three quarts?  Return the fourth for a refund.  Nothing hurts more than saving expensive left-over paint and the like, only to throw it away in a few months because it is no good.  You had good intensions when you saved it, it just didn't work out in your favor.

Epoxy is your friend.