For a Nikon camera? Depends on what you want to shoot. You can never go wrong with the 50mm f1.8 or f1.4. It’s a well rounded lens for portraits or a basic carry around lens. Since it has such a small f stop, it allows more light to enter through the lens giving you a lot of bokeh ( the blur ) in your photos. This works especially well if you want to focus mainly on one subject. The 50mm is relatively inexpensive. You can find used ones for about $100 on Amazon. :)
I don’t use any editing websites, however, if you can get a hold of Photoshop or Adobe lightroom then those are really good photo editing soft wares.