I'm tempted to start AC, just because I can probably pick up the first one for cheap.
My advice is:
1. Play Assassin's Creed now- Skyrim can wait.
2. Pick up AC1 on the cheap and burn through it as quickly as possible. Just stick to the main quest, don't bother with all the sidequests or collectibles. It's a fine game, but don't waste too much time on it I say this because...
3. Assassin's Creed 2 is amazing. SO much better than AC1. AC1 is just a prelude to the greatness that is AC2. Just far more interesting, varied, engaging, complex, fun. Also very cheap at any 2nd-hand gaming store. You can spend a LOT of time in AC2 and AC:Brotherhood. No need to rush to AC:Revelations- just take your time with AC2. Great stuff.
4. Wait a year or two and Skyrim and AC:R will both be super-cheap 2nd-handers.