You get the reward after the event is done. If the overall goal is achieved too, you get free Victory and Commendation packs. Sometimes it takes a few days after the event is over. I had one that took until the following Thursday after one of the ME3 events. There is a new multiplayer DLC coming out on the 29th, it is free if you have an online pass for this game. Play a lot this weekend, and save your money until the DLC comes out to buy Spectre and Premium Spectre packs from the shop. Then you might be able to snag the new classes or weapons.