Learn to purl. Yes, you could go full vintage (early 15th century Europe) and knit everything in-the-round, without ever purling. You could. But in my opinion, this would be a pity.
Purling allows you to knit flat. Including purl stitches in knitted-in-the-round garments enables you to create an infinity of textured knits.
Ribbing is created by a succession of knit and purl stitches (often 1 knit followed by 1 purl or 2 knits followed by two purls – mentioned in patterns as K1/P1 ribbing and K2/P2 ribbing, and sometimes simply as 1/1 or 2/2 ribbing). Being ablt to follow ribbing indications is tremendously useful as ribbing is a very simple way to create garments that fit at the neckhole, on the cuffs, etc. whilst also adding some extra stretchiness.
Now, just as for knitting, there are many different ways to achieve a purl stitch. I suggest you try out a couple of them then pick one up and exercise it until you manage to create an evenly tensioned fabric. As with knitting, be patient troughout this learning process. Cheap yarn then to split and that is especially an issue when you are trying to learn how to purl. As for knitting, go for yarns that are at least on the higher end of low price tags.
I am a continental knitter, which means I am a picker and hold my yarn in the left hand. Many (most?) continental knitters have their thread tensioned in front of their knit when they purl. I don’t. The way I purl is called “the Norwegian purl”. I favour this purling technique as consistently tensioning the yarn thread on the back of the knit helps to create an even tension. But that’s the way knitters are : they always have a very good reason to favour the technique they are most at ease with. If you are no longer a beginner, be brave and experiment with different purling techniques. You might find some unsuspected benefits. I, for instance, found out I prefer knitting P2 with the throwing method as I achieve neater results.
On a side note, this Norwegian purl is how I learned to knit at school in…… Switzerland, taught by a Swiss teacher. And I’ve seen videos of Norwegian knitters that defineteyl aren’t using a Norwegian purl. Knitting terms are not to be trusted as being an accurate description of how people knit/purl. British folks at times indulge in a rather insular mentality and they refer to the rest of Europe as “the continent” as if they themselves weren’t part of it. In knitting, “continental” is thus the opposite of the “English” method for purling or knitting. And yet…. French people knit the same way as the English do and people in Europe, even when using “continental” knitting, use rather diverse methods, as the “Norwegian” purl situation demonstrates.
Knittinghelp.com has a good page on the purl stitch which includes videos all the different methods of purling (continental/German method, combined, English/Throw method, “Norwegian”, back knitting).
Unsolicited Knitting Advice 