I agree with Needa. Use the camera and lenses you have for a while and learn what niche you really are interested in. That will lead you to what lenses you will need. As she hinted, there is a danger of buying lenses for the crop sensor DSLR you have now, and then you find that you want to move into either full frame or mirrorless. I started with film cameras, got out of the hobby for decades and then got back in with a D3400. I quickly found that I wanted to "move up" to something that suited my style more and got into a full frame mirrorless. All the camera manufacturers are moving to mirrorless, and Nikon is no longer developing any new DSLR models.
If you do buy another lens/lenses for your D3400, consider a full frame FX lens. That way you will be able to use it with either a full frame DSLR, or a mirrorless using an FTZ adapter.
Despite being a consumer grade camera, the D3400 is capable of producing quality images as long as you do your part. There is no way you will be able to tell any definitive difference between the images from my D3400 and my Z5 full frame, aside from low light performance.
Learn your camera. Have fun with it. Try lots of new things with it, and you will likely find your place and where you want to go with your photography.
