You don't need much 20 to 30HG is good. I have just started using a vacuum pump and its great. I got the cheapest one at harbor frieght with the 25% coupon it was around 75$. made up a couple of carboy tops out of the ornge two vent covers, got a vacume canister for about $10 to keep a safety between the pump and juice (its important).
Its so easy now to transfer and degas, and it dose a fantastic job.