Okay, so you have now hit max level, should have some blues here and there, still got heirlooms. If you leveled without heirlooms then you're probably already ready, assuming you have the right gear for your spec (e.g. agility gear for enhancement shaman).
To get the preraid gear you need you are allowed to run classic dungeons (you will have to do these using the specific selection as classic random disappears). You are allowed to run these using heirlooms if you wish, but as long as you get your preraid gear to replace them it's all good.
If you are struggling to get a certain slot filled (e.g. rings) you may buy from the auction house if you wish. But Remember! You must only use vanilla gear and TBC gear is not allowed so check where the gear comes from on somewhere like wowhead before buying!
We hope to be raiding with you soon!