Welcome, new player. I have a few tips to make your gaming experience better.
1. Don't get invested in your first character. Heck, don't get invested in your tenth character. Your first dozen or so characters are for you to learn the game's mechanics, rules, class mechanics, your playstyle, etc. You are going to make a LOT of mistakes in specialization choices before you find something that works for you, so don't be afraid to delete a character you don't like. This also means you shouldn't spend cartel coins in a character that you aren't going to keep either. Until you find a playstyle that works for you, don't get invested into a character.
2. Read the manuals and in game codexes. I've seen a LOT of questions that other players get frustrated with that could be avoided by just reading the in game codexes and manuals on the website. For example, if you want to know what gathering skills go with a crafting skill, read the crafting skill's codex. It tells you. And you can find ALL the crew skills, both crafting and gathering, on the fleet for ease of access.
3. Do NOT press Alt+f4. That is a Windows code for "kill program", and your game will be be closed down. Don't fall for this.
4. Moddable gear is available to both f2p and subscribers. Use it. You can tell moddable gear by the orange border around the item, and your planetary commendation medals are there for a reason, and can be used on any planet. So just because the upgrades on one planet are below your level doesn't mean commendations can't be used on another planet. Also, despite what the in game codex says, you can mod your gear on the fly. Hover over the item, and if it's moddable, it will show you what you need to press to mod it.
5. While there is nothing wrong with grouping up with your friends to complete a quest, if you are having trouble with a story mission, you are underleveled and undergeared. Go back, upgrade your gear (preferably with better mods), grind out a level or two, and come back. If you're at level, the fight will be tough, but winnable. If you're overleveled, it will be easy. Story missions are designed to be soloed, so if you can't survive a story mission for your class, you won't survive later. Trust me, I found this out the hard way when I was still f2p.
6. The GTN is your friend. If you've got enough credits, you can get some good gear off the GTN. Heck, you can get mounts that upgrade with your speeder skill, saving you a lot of credits in the long run! I have bought both the upgradable speeders and modable gear that I will like looking at for the rest of the game. It is an awesome thing in the game, and people normally put things on there at reasonable prices.
7. Don't be afraid to mix and match your mods. On all my characters, I put DPS focused mods, that focus on my damage stat, in my weapons, and endurance focused mods in my armor. It increases survivability and doesn't hurt my ability to do damage.
8. Don't be afraid to ask questions, but make sure you look for it first. If you're not asking a question that can't be easily referenced, experienced players won't treat you like you're a moron. Things like "Which specialization fits my playstyle?" are things that people will happily help you with. "How do I use the map?" Will get you derision, but it's still a good question, because IRL, learning to read maps is becoming a lost art. "I'm new to MMOs, what does this mean?" is another good question to ask. People will help you. Just learn to sort out the real advice from the trolls, and you'll be fine.
9. Most importantly, have fun. Do what makes you happy in the game. None of these tips matter if you're not having fun.