Yes, get conditioner. Depending on your hair, you might have different needs. The more you style it, dye it, and do things with it the more you need conditioner for your hair. With longer hair, you need conditioner to help your hair keep strong, and not all split-ended and breaking.
If you're growing it out, getting it cut and styled is a good idea. I know that that sounds counter productive, but it actually is good because it dispells split ends and your hair won't look unkempt as it grows out. If you tell your hair stylist that you're growing out your hair, he or she won't cut a lot off, but will style it with layers and even your hair out. This makes your hair look good through-out growing your hair longer.
I know too many people in the trans community that just try to grow their hair out without ever cutting it -- it starts looking bad pretty fast.
When I grew my hair out, I got it cut every couple of months or so (shorter hair, you need to get styled a little more often). As it got longer, I didn't need to get it styled as much. Even when it was long (I had long hair for 2 years) I still got cuts at least 2-3 times a year to get rid of aweful split ends, even out my hair and add layers (helps with volume, look and style). My hair looked great!
Last year, I shaved most of my head and just kept long bangs in the front (me being punk LOL). I've been growing it out since then, and now it's longer. I've had it cut a few times. Only twice, however, 'cause I cut my hair just before SRS and after SRS it took a while before my hair started growing again (in some people, after a major event or surgery, you can get affects like hair not growing). It's growing really fast now. But, still need to get it cut and styled and I need to take good care of it with a good shampoo and conditioner to make sure my hair is strong.
Well, styled and conditioned hair makes a huge difference.