IMHO, unless you are an experienced user who does regular heavy bag work a 70lb+ vinyl will do the trick. Easy to clean and repair with duct tape. If you are doing leg work (Muay Thai) get something 4’6" or more. On the subject of gloves these are a must. If you use a heavy bag barefisted you run the risk of messing your hands up, wrecking your shoulders and seriously compromising your technique.
Ran