This is an opinion-based question, thus the answers you receive will only be opinions. What do you want to do with the car? What do you think it lacks that could be changed via modification? Many people start with the Cobb Accessport or some other Stage 1 tune, but others focus on tint and in-car audio. Some do tires while others do sway bars.
Figure out what you think needs to be changed and then take a look through some of the topic-specific sub-forums to determine what your best approach might be. Searching here can be a HUGE benefit as well, since this is a topic that has been covered a LOT.