You need to narrow this down a bit. Being more specific as to your needs will help everyone recommend a good solution for you.
Are you just wanting something to hold your gear while inside the vehicle? In that instance, a hard case or square bag would be more appropriate. Or are you wanting something that you can grab and take along with you outside of the vehicle? Usually then a backpack or slingpack is needed.
Is there a type that you prefer over another? Backpack (bothshoulders) vs. slingpack or carry bag (1 shoulder) for example?
And Jack brings up a good point, too. You will eventually acquire more gear, and new bags ain't cheap! You want a storage solution that is actually bigger than your current needs so that you can grow into it.