Well, at my last lesson, my instructor decided I should start using a crop. I'm still just a beginner - been taking lessons once a week since February - but it still made me feel sort of bad. I'm doing posting trot, and having a very hard time keeping the horse at the right speed/pace while doing courses and turning. I haven't gotten the hang of post/kick/post/kick, I think. It's like my body won't cooperate or coordinate at the level I need to communicate with my horse.
You'll get there. It took me a solid year before my posting was any sort of respectful.
I'd be able to communicate everything with just my body and not need anything additional. I whined (lol) to my instructor that I really didn't want to use a crop, because it felt like cheating and/or training wheels
But here's the thing though: at your riding level, your bodily communication skills are not nearly sharp enough to use on their own. Riders must first hone all of the basics and develop independent hands, seat, and legs before communication can become refined. To be honest, using a crop is probably more clear to your horse than whatever sort of confusing things you are doing with all your limbs! (I mean this in the most endearing way, I promise).
Everyone is always in such a rush to get better, but the honest to goodness truth is the only thing that will make you a better rider are hours upon hours in the saddle. While watching videos and reading certainly isn't doing you any harm, what you need most is patience and practice. Time. Lessons every week, multiple times a week. Add those lessons up and the end of the year, and reflect on how far you came. You will be utterly and positively shocked.
Don't worry about your horse. Lesson horses are there to teach you, they're used to this stuff! Using a crop isn't in any way cruel, unless you are using it for blatantly abusive purposes, and a lot of those lesson horses have much more woah than go and almost require them. It's what makes them safe for novice riders such as yourself, but that often means they need a little more encouraging because they have learned that they can putt along with very little effort - because riders like you aren't going to correct them and tell them otherwise!