As a general rule, if you can only ever have one ship at a time and want to do a variety of roles, you want the multipurpose ship. The progression here is Cobra MkIII -> Asp Explorer -> Python.
If you prefer to stick to combat only, get a Vulture -> Fer de Lance
If you prefer to stick to non-combat trading and delivery, go Type 6 -> Type 7 -> Type 9 ... although be warned that the latter two are quite slow, sluggish, and WILL get destroyed often in Open if you play there.
Then there's also the faction based ships. Empire ships are best at multipurpose roles and flying at blistering speed. The Imperial Courier, fitted with performance drives, is currently the fastest ship in the game when stripped down. The Imperial Clipper is legendary for both it's beauty and sheer speed for it's size. Federation ships tend to have really good armor and weaponry, but poor jump ranges. The Federal Dropship is a pretty good medium trader that can also do combat quite well. The Federal Assault Ship is VERY agile and also a dedicated combat ship.
Honestly, the best thing to do is simply build some ships and add up your credits in one of the many ship building tools available online. My personal favorite, currently, is Coriolis:
https://coriolis.edcd.io/
One thing, though ... whatever ships you end up choosing, you WANT an Asp Explorer. It is the most useful ship in the game, hands down, due to it's reasonable carrying capacity and spectacular jump range. Pretty much everyone here who can afford it has one in storage.