Well done on completing your first 10k, what was your time? Hope it is the first of many for you!
I entered my first hm in September and found that I really benefited, albeit perhaps only psychologically, from eating a couple of jelly babies after 3, 6 and 9 miles. This also gave me a yardstick too, a small carrot to dangle in front of myself!
I ran carrying a small hand held water bottle and I liked the freedom it gave me to sip as and when rather than relying on drink stations.
I tried gels but the ones I tried made me feel sick, they didn't taste good to me, but e be ruined has different preferences here. Try a few different ideas, gels, isotonic drinks, water, sweets and see what works for you. Then stick with your chosen combo for a few long runs and remember the golden rule, don't try anything for the first time on race day!
Good luck for the hm, when is it? Do you have a goal in mind?