There is tons to do. Once you get to your main city (Qeynos or Freeport), asside from all the "busy work" stuff, the most important things to do for remaining competative are: upgrade your spells/abilities, upgrade your armor and weapons, and make some food and drink.
Sounds weird, doesn't it? But even if u can summon food and drink, don't. Player made food, when eaten, gives u a health regen buff that's noticeably good compared to all other food - drink does the same for power.
Use this site's quest guide to "cluster" quests - to do them more efficiently. And make getting a good new weapon and new armor a high priority. This can go pretty fast.
Visit the scribe shop or trainer in your town right away. Buy "apprentice lvl 2" upgrades for your main spells or abilities if you can. If not, start saving for these right away. App lvl 3 is better - and is player made. Find a broker and see if u can afford these in key areas. Joining the trade society (a trap door - ask npcs at these until u find the one who will let u join) lets u access a broker - u can use him to buy from other players. Or you can use the market board in your apt to find stuff - and go to those players to buy. Upgrading spells/abilities makes them to more (more damage, or more healing - or they buff more, whatever).
The ranks are apprentice 1, 2, 3, Adept 1 and 3, and Master 1. U get app 1 automatically. U can buy app 2 from scribe /trainer. App 3 is player made. Adept 1 and Master 1 drop off monsters. Adept 3 is player made. You don't have ot buy in order. If you see an adept u can use for cheap, u can buy it and scribe it and use it, skipping app 2 and 3.
Knowing these basics will help u keep up, even if u don't have much time. GL