I'd suggest deff. a 100 lb. bag. First bag I got was 70 lbs when I first started, and it got useless fast. Ended up having to go out and get another 100 lb one in what seemed short order.

Not sure the weight deal, and it might help for a lesser weight the chime in as i'm heavier, but most anyone I know regardless of weight uses the heavier 100.

Good luck getting a bag.