i think it really depends on how long you can stay on line, buying and selling players is still the fastest way to make money, market values change constantly - as a rule of thumb, prices generally become higher when playoffs are about to start and prices go lower when they are about to end.
training players can also be profitable, it can also yield good profit especially if you concentrate on one and two position
training but they take a lot of time to do, try to train allstar (potential) at the very least, they are easier to sell and look for 18 year old prospects if you want to do this - guards usually have higher value than big men so you have the right idea - if you really want to maximize your sale, i suggest training Outside defense they have tremendous value because they are very few in the transfer list
never spend on the draft what you cant afford 10k is the most i have spent a week on the draft! if you are looking for prospects count 3 days after the draft and you will see a lot of teams selling their draft picks, since you are new team, try selling most of your players and converting them to cash you will need a lot of cash to be competitive, good luck to you.