Filament

Depending on what your 3D printer came with for a stock build platform, upgrading to a
Glass bed might be a good option. Removable magnetic beds with auto bed leveling are a new favorite of mine, but if your printer didn’t come equiped with one, then I think
the new best approach would be to upgrade to glass.
The link is to a plate for the MonoPrice Mini Delta, but if you search your printer in Amazon, you will likely find a glass plate made to fit your printer, because this is such a popular upgrade.

After a glass plate the 2nd most common mod would be to upgrade our hotend. With this you will likely find many options and a search for ‘YOUR PRINTER NAME’ +HOT END, will likely produce may results.
E3D is the leader in the hot end space and I can strongly recommend the products. Buying these from Amazon can be a bit spotty since it is easy for clones to jump on the listing so your best best would be to get if from their US approved distributor Filastruder.