The [Brick] Abyss supports the following LEGO User Groups. If you want to get involved in more serious building and doing exhibitions, you should try to find a LUG near you.
Here are some resources we use for building that are mentioned somewhere on this site:
To buy individual LEGO parts (including parts in rare colors or parts that are not currently being produced) check BrickLink. It is an online platform of individual sellers. At the heart of it is a data base that lists (almost) every LEGO part ever made, including different color versions and sets it appeared in. It might get some time getting used to the terminology but you will not get around BrickLink if you are serious about LEGO building.
For digital building you can use LDraw (more professional, more complex builds possible but also more difficult to use) or LEGODigitalDesigner (easy to use, drag & drop). For digital layout planning we use BlueBrick.
These abbreviations are common in the LEGO community (and you’ll find them on this site because it turned out to be impossible not to use them):
LEGO = LEg GOd (Danish for “Play Good”)
AFOL = Adult Fan Of Lego
LUG = Lego User Group
MOC = My Own Creation