Hey, welcome!
M, A, F, FA 50mm f1.7 lenses all follow the same optic design, with relatively small differences (mostly in coatings and shape of aperture blades), so you will not find huge differences in optical quality between them (though, some claim the F series is sharpest). Oh, and the DA 50mm f1.8 fits this as well. The main difference between these lenses is the construction and automation. The M series has no automation at all. It is beloved on these forums because it is a good, sturdy lens for a really low price, even though the prices have risen lately due to its popularity. The A series has auto-aperture, which is a very useful feature! It lets you choose the aperture on the camera body instead of only on the lens' aperture ring. F and FA series allow this as well, but they also have AF! Finally, DA series is full automatic just like the F and FA, but it doesn't even have an aperture ring (which limits its use on older film bodies).
tl:dr; Get A series lens for ease of use. Get F or FA if you want AF. But honestly, the DA 50mm f1.8 is so affordable lately, it might be worth to just go for it. You get the most modern lens coatings, AF, full automation, and warranty. Sure, it is plastic, but it is still durable and much lighter. The amount of force needed to damage the plastic would probably bend or chip the older series lenses as well. I like my M 50mm f1.7, but it is not for the faint of heart. Its for hardcore users, who enjoy an old, metal, manual lens. If this fits you, then go for it
If you get a good copy, any of these lenses will be great. The question is just how much automation you want, and what a good deal you can find.