I would get either level 1/11/21 venom, cause those are the levels when the duration goes up by one second (damage applies once more). Venom 11 is decent for training, and if you want to boss, then there isnt likely going to be the disadvantage of not having MW, as chances are someone else will have it.
EDIT: although, if you plan on using a weapon that requires you to have MW, it would be a good idea to either get interchangeable luck/dex capes/another gear, or just to simply not do it. It would be opitmal for bossing with those with MW, although more expensive.
EDIT: although, if you plan on using a weapon that requires you to have MW, it would be a good idea to either get interchangeable luck/dex capes/another gear, or just to simply not do it. It would be opitmal for bossing with those with MW, although more expensive.