My biggest mistake was expanding too early, too fast. I didn't know what would work... and I just modeled what was packaged in 'whatever looked cool' instead of what would work.

For example... I started back in 3rd edition, and I bought a command squad. I modeled the 'space marine captain' as my HQ just as it was packaged: a storm bolter and power weapon. I did not realize that for the blood angels, it would have been much better to use a bolt pistol or plasma pistol to get the +1 attack.

Also, when you have a lot of models, it makes it that much more difficult to paint. You get them all, then start painting, and may get a bit overwhelmed or disheartened. That is what happened to me... I think I still have many models (that I don't use) that are unpainted.

So... start small. Paint what you have. Learn how to use them. Think about strategies. Then, when you are ready to 'expand' get something else. It is good to read up on information, such as these message boards, to get an idea of what other people like to play. However, ultimately you should play as best suits your style. Just because a lot of Blood Angels players use Veteran Assault Squads does not mean you should just ignore Terminators. Especially when our Terminators cost the same as a 'Vanilla' Terminator Squad... except we also get a 'free' Death Company member (roughly 30 point value).