depends what your goals are.

3 shamans work well, they have good dps and are easy to set up.
If you try and do only dps you'll have long dungeon queues. 2dps+1heal will be much quicker, and is very viable with 3 shaman as well, but you'll definitely need a couple more players to do instances correctly.

If you want to do something a bit challenging, then maybe do a full tank+dps+healer group.
maybe a paladin + 2 shaman, or something like that.

all instances at lower levels are fun to do, just use the Looking for group tool and you'll be ported there as soon as you can.
Most of the fights in those instances are very simple, and can be done with not much hassle