Cheap UB need suggestions

i dont have any of the planeswalkers, only a few of the lands, and am missing some other things, and i really want to pull off this combo in a sanctioned match. also dont have more mana leaks right now, or they would definitely be in there. this deck fears creatures slightly less than some control decks because my blockers get more powerful as the game goes on and then tap for enough mana to just lock up the game later. stabbing pain may be weak, but tapping the creature means that you can prevent titans eldrazi etc from attacking, giving you an extra turn to go off, and it takes out x 1 creatures like lotus cobra, pulse tracker, bloodghasts (for a little), and almost everything in boros.