Is there any way to get practice drawings with dimensions so i can practice making things on Inventor.
You could pick anything around you and, caliper (http://en.wikipedia.org/wiki/Caliper) or at least ruler in hand, start measuring it and sketching->making operations over sketches. If you need to learn dimensioning according to standards, let me know and i'll give you some standards numbers for you to check.
Tiff drawings with dimensions from Solidworks
You can find many by searching google. If you browse machining forums you can find a lot of drawings under sections of the forum reserved for quoting. I also wouldnt mind emailing you some drawings of tools ive designed however i dimension drawings concisely with ease of manufacture in mind and try to steer away from ambiguity because i am a machinist. It isnt often i design to a standard. That beong said im sure you could ask around here more.