How do I decide what optional items I should buy to crochet?

Answering the question "do you care to know what you're doing?" will decide many things for you. If you cannot or do not care to "read" crochet, you will probably need row counters and row markers at some point.  Even if you can "read" crochet, if you cannot read it well, you will probably need them for dark or fuzzy yarns—or want them, if you can read it well but prefer to avoid the headache. A simple alternative to a row marker is to tie a contrasting piece of yarn can be tied into the row, which can be removed later.

 

When determining gauge, if you can count stitches easily, you need not get a gauge ruler, but if you cannot see so well, or if you are crocheting a yarn that is difficult to count by feel, then you might want one for accuracy. Also, some people use straight pins to help with this, marking the origins of counting.

 

Notice the purpose of each item. If you do not work with more than one yarn, or if you do not mind untwisting between two skeins, yarn bobbins are unnecessary. You can also improvise your own with a cut piece of cardboard.

 

A size gauge is never necessary (unless you get a hook without a size on it), but it is always helpful for project size purposes.

 

A pencil pouch could also suffice for a hook case, if you are so inclined. There are other options, though some like giving each hook its own slot in the case.

 

Unless you like them, hook cushions, point protectors, and stitch holders are also unnecessary.

 

You decide what you want.