Your area may differ, but most people sail in areas where the average wind is between 6-12 knots. So you want to race a boat which was designed from the get-go to excel those average conditions. I can't tell you how many times I've heard, "Well... it really wasn't my boat's conditions..."
The best way to win in handicap fleets like PHRF or Portsmouth is to get a boat that is well established in your area with good intrinsic performance, then prepare it and sail it better than the competition.
Let's break that down:
Established in your area
You want to take any controversy away from the boat's rating. A boat with many examples across many areas (and especially local popularity) will not be subject to competitors 2nd-guessing the fairness of your handicap. e.g. a J/22 is a J/22 is a J/22 and everybody knows what they rate and how they perform. That way, when you start winning, no one can say, "Hey! They have a cheater rating!" Over and over again I see owners try to buy trophies by having the fastest boat. Handicap racing doesn't really work that way. If you have a rocketship but there is no equal boats to lock in your rating, you will keep getting bumped in your rating until your performance falls in line with expectation, which is highly subjective.
Good intrinsic performance
You want a boat that is a good sailing boat. This might seem obvious, but many successful race boats are not all that great but by force of will and effort and by throwing money at them and by favorable rating, can be made to win. The old saw during IOR was "Rate low and go slow." You don't want this. You won't enjoy winning on a slow boat as much as you will enjoy sailing a fine boat.
Prepare it better than the competition
So you've got a boat with a rock-solid rating that sails nice. The guy right next to you on the starting line has the exact same boat. How do you beat him? You make sure your boat isn't loaded down with cruising accouterments, has a clean bottom, and has great sails. Clean bottom and great sails will put you on the podium every time. In your budget, the sails should be the biggest item in your budget.
Sail it better than the competition
And so it comes to this. Practice. Don't throw away distance/time on botched maneuvers, misunderstood rules, or bad sail and boat trim.
Most of my beer-can racing is in a harbor surrounded by homes at least two stories tall. In this venue, mast height is absolute king. You can have the slickest hull in existence, but if your mast isn't up there catching the breeze above the houses, you will be fighting for speed every inch of the way. A slow hull with a tall mast will beat a fast hull with a low mast every single day in Newport Harbor.