These days you can buy a variety of types and styles in a range of prices and with a few notable exceptions they all work in essentially the same way.
I learned to spin on bottom whorl spindle but tend to use top whorl spindles now. If you know the difference you'll also likely know what you like. This design can be used either way or can be switched between the two styles if you find you need one or the other.
Spindles can be purchased in stores or online for anywhere from $15 or $20 on up to ...a lot. Especially if you want antique or custom "hand crafted" spindles. On the other end of the spectrum you can make them out of rubbish and free things for literally nothing but time.
This will show you how to make a decent looking functional spindle for a few bucks. About $2.50 in this case.