They’re pretty good for a start, just keep practising and you’ll continue to improve, as we all do!
A 50mm 1.8 lens is a good one to begin with, as it works well in low light, and for the low price you really can’t go wrong. The D90 is a solid body and should do you well until such time as you can afford to upgrade.
Good lenses are worth their weight in gold, but they also cost a LOT. The lens I get the most use out of is the Nikon f/2.8 24-70mm. It is fantastic! I also have the 70-200mm lens which is also beautiful, but both of these are really expensive so they would have to be something you’d look at getting later on. They’re also FX lenses, and the D90 only requires DX (though you can use full frame ones too).
For something that is more of an all-rounder, plus is quite a lot cheaper, how about the Nikkor AF-S DX 18-300mm f/3.5-5.6G ED VR lens. This would give you a great variety in zoom range, from wide angle to really close-up. Obviously this lens isn’t going to work as well in low light, but for general outdoor photography and travel it would be useful.