My advice is to spend money on a quality sleeping bag first. You have enough budget that you can get a quality down sleeping or quilt, but it would leave much left for a tent.

Have you thought about renting some gear (like a tent)? It's a good way to find out if this sport is for you before spending large amounts of money. It is not a great idea to spend large amounts of money until you know what you want. But.... I've never met anyone who has regretting buying a quality down bag. They also hold their value well if you decide to sell it.

Are you going with anyone else on your first outing?