You won't be able to do very much in a heroic raid for a long time. I've just turned 83 level wise and I can still just about only post 1 mil + score in one go on Rancor but last month it was half that.
That said, once you get even a single 7* you'll be able to at least post a zero as you'll be able to join the raid. Everybody needs gear and tokens so nobody minds if you "freeload" for a bit.
It's worth even posting a zero, especially for heroic raids as then you can get raid exclusive toons. Apart from heroic Sith, as anything to do with that raid is terrible and nobody should play it.....at all.....ever.
Majority of toons are pretty easy to get to at least G8, after that you'll start needing proper raid gear.