If your grasp of the grammar is good, we suggest the following online resources to increase your vocabulary and overall proficiency:
You can get started by getting an Online Diagnostic Assessment (ODA) here:
http://oda.dliflc.edu/ (You'll need to create a free account). The ODA system will let you know where you are (you are shooting for a 1+/2) and will select custom materials to get you there.
There are also around 279 reading lessons freely available from the Defense Language Institute's GLOSS: