Your store should provide lands, so just use theirs this way you dont get mixed up on which are yours and which are the stores
Whisper the chosen word: Tap enchanted creature
For one black mana and a few sacrificed Squirrels, you can give any creature +X/-X, either pumping up one of your creatures a bit or taking down your opponents commander at the cost of a few creatures.
This one is Light Played, so quite affordable
: If Frodo is a Scout, it becomes a Halfling Rogue with "Whenever this creature deals combat damage to a player, that player loses the game if the Ring has tempted you four or more times this game
Making copies of spells will not increase your storm count (unless the copying effect says that you cast them), but it can massively boost your potential resources to continue playing other cards