“First I'm waiting for a reply to join a faction. ”
Remember that it takes a real person to accept you into the group. Also, please make sure you're joining properly. Darkness messaging someone isn't really joining (I've known some newbs to do this).
“Then I'm stuck in Mos Eisley. How do I leave Tatooine ”
Either hire a transport group to move you or ask your faction when you're accepted. Most factions do try to "rescue" their members.
“or get a local job, ”
Local jobs aren't added to the game. You're only able to work for other players/factions.
“when I have enough credits, buy ships ”
Go to the RPG Centre link for the traders areas, the #SWC-Traders room on IRC, or swc-gm.com