There are a few neat ways to do this. As others suggested, there are freebie stores. One more recent addition is Fab-Free, aka Fabulously Free in SL. Their site also links to a great full list of places offering freebies. Some are geared specifically toward new residents under 60 days old. This is my BEST pick for new people, as the freebies are more updated than some older stores.
Also, many stores offer free gifts to people who join their groups. To do this, go to their in world store, and you'll need to subscribe to their group using an object in their stores, usually located near the door, or a desk if they have one.
I'm not sure if it's still around, but there is a store called the Gnubie Store. They offer free and low priced items.
Lastly, if you prefer to earn money rather than rely solely on freebies, you can look for stores that offer employment. Some are customer service, some are clubs looking for dj's, hosts of events, or even dancers (dancing tends to be more adult content). If you have some money but not enough to buy expensive clothes, some stores have sale rooms/outlets, or even short term sales going on that you can take advantage of.
Hope this helps!