Htown's Tips for Being a Cheapass Non-Sub at SWTOR
1. Most unlocks can be gotten from the GTN for less than the free/premium credit cap, including crew skill slots, server slots, inventory space, legacy unlocks, etc. Before you buy an unlock, make sure there isn't a more expensive (but still affordable) "Account" version of the unlock, which can apply to all of your characters.
2. Buying Speeder Piloting II (for increased speed) from the class trainer is a waste of money. If you save up like 20,000 extra credits you can buy a Speeder piloting III from the GTN. Don't buy a speeder from the speeder vendor either. You can get a mount that auto-levels with your speeder piloting skill for between 8k and 20k on the GTN.
3. Don't bother with weekly passes until you're at the level cap. Run a maximum of one flashpoint and two warzones per day to maximize your rewards.
4. Don't buy a third crew skill. It'll be much easier on your character's wallet if you just buy the necessary crafting components as needed from the GTN, at least until you get towards the cap. Of course, it's cheaper not to bother with crafting at all, but certain skills are decent for making money on the GTN.
5. Bioware doesn't want you to use the mail system as a free player, which makes it hard to transfer money between characters. The way around this is to have the character to whom you want to transfer credits put up a cheap green item on the GTN for the amount you want to transfer (which should be way way more than it's worth), then have your rich character buy it.
6. Don't buy gear from the GTN, as you'll be outleveling it soon. One exception is for new companions, which will join you with entirely empty slots. If you want to use them immediately, buy a cheap green piece of equipment to go in the slot.
7. At some point, you are going to have to spend money on the game if you want to have any fun at the level cap. My recommendation at this point is to either buy the expansion, or spend 5 bucks on cartel points and get some stuff from the cartel market. Either of these will lift you to premium status, which will raise your credit cap from 200k to 350k and give you access to a cargo hold (bank). Once you get up to 350k credits, you'll want to look on the GTN for an Artifact Equipment Authorization. This will allow you to equip purple gear, which you'll need to progress at the cap. You may have to check back from time to time in order to find an AEA you can afford, because some people like to be dumbasses and list the authorizations for more than the credit cap.