Well your friends are evil, Venice is the hardest civ for multiplayer, and is a hard civ in single player too. Though yes you can buy your way to victory, buy science buildings, food buildings, and workers, build farms on flat lands, mines on hills, and lumber mills in forest.
Focus military techs, then buy military buildings (barracks, armory, etc.) then buy units. Wait to be attacked, then defend, widdle them down as they keep attacking you, keep in mind they'll build more units, but not as many as you should be taking away. Then, whilst keeping some units around your cities, start the offense, this will either go well as they used all/most of their units on you, or terribly as they used some units on you to make you think they suffered heavy losses, then wreck you when you get to their lands.
I would wait till you have ideology (if you can), then I'd go autocracy and get lightning warfare, landship/tank armies are insane.