Regarding costs, I wouldn't be penny pinching when buying gear. Quality doesn't cost, it saves.
I have always mostly bought the best gear for the job for that which it's required for, seriously, in any one trading day, my positions can easily gain or lose into the thousands of dollars.
I say to my wife, don't scrimp when buying groceries, your job is to buy what's good, my job is to bring in the bucks, don't waste time saving a buck, it's my job to be efficient due to the large amounts coming and going in trading.
Therefore my suggestion to you, buy the best within reason, and more importantly, hone yourself to be a good trader. Don't build your own computer, waste of time, TRADE WELL! That's where to spend your time.