Having a patchy beard or beard patches is a very frustrating thing, but sometimes you are your own worst enemy. A beard takes time to come in and what you have after a couple days of growth can be completely different than a few months of growth.
The reason is that beards grow in at different speeds and when you give a beard enough time to grow properly those patchy areas will fill in. That being said, there are some beards that simply will never fill in - no matter the amount of time you give it. For those people the best strategy is to keep your facial hair short or scruffy. Many celebrities keep this look like Johnny Depp and James Franco. There is no shame in a beard that doesn't fill in fully. The shame is trying to be someone who you aren't. Celebrate your genetics and handle it to the best of your ability.
The third kind of patchy beards are those guys who have full, dense beards but find the smallest imperfection and assume it's a shit beard. The reality is their expectations are too high. Only a small percentage of men are able to grow a completely full and dense beard. It's best to try growing out your beard before you go around telling everyone that your beard is patchy. You only know if you grow.