The are two main types of fly fishing flies, wet (sink underneath) and dry (float on top).
If one were trying to learn how to how tie the flies yourself instead of buying them, would one type be easier to start with rather than the other?
The fly patterns used in modern european nymphing are purposefully simple and effective. The philosophy behind these patterns is to suggest the shape of the insect instead of trying to perfectly match the hatch, and this makes them very versatile as well.
Patterns like the tungsten torpedo:
Or the tungsten surveyor:
Are extremely easy to tie and very effective.
For dries, the CDC and elk:
And the F-fly:
Are very simple and do a great job suggesting caddis and mayflies of various types when tied in different sizes and colours.
The easiest fly to tie is probably an egg pattern. The fly requires a hook, high tensile thread, head glue and either a marker or a small amount of flash. This fly may take ~20 minutes the first time tied and can take <5 minutes after tying ~5 flies. It’s a great fly to begin with as you do not need to worry about a multitude of materials and managing sometimes fragile feathers.