Without a doubt, the first layer of any print is the most important. If your first layer does not stick well to the print surface, it is very likely to detach later in the print and cause the print to fail.

Make sure to watch out for:

Warping Increase your bed tempurature. If you have an enclosued build chamber, use it. Try to avoid printing sharp lines/corners on your first layer. Try a brim, skirt or raft.

Dirty Bed Make sure there isn't debris or plastic residue on your print surface. Wipe clean with alcohal after every print for best results.

Build Surfaces There are lots of different build surfaces out there as well as adhesives. Glass, PEI, buildtak, hairspray, 3D gloop, magigoo, and glue stick are just some of the options. It mostly comes down to a matter of personal preferance, with the correct settings and proper first layer, most anything can work!