Throw away whatever you don't need anymore without hesitation. If you manage to do so, congrats on your first step to success.
Rearrange your stuff according to categories for easier search. You can also sort them aesthetically.
Come up with a theme before proceeding to place your stuff. You can also design according to the things you have. (Why this is step 3 instead of 2: There's a high chance of you wanting to redisplay yr stuff despite already having a design in mind, so XD)
Do this step only after you have completed the above steps. Add assortments or DIY to touchup!