So, I keep seeing these things on websites about character development and other people here that I should probably have a big goal Luke needs to achieve, and that a lot of things he does will directly or indirectly lead to that goal. I have a bunch of smaller ideas, and specific things that happen that cause character development, but I can’t come up with an end goal for him to reach. Does anyone have advice?

The beauty of RP websites is that you have creative freedom to do whatever you wish with your character! While having an ultimate "big goal" might help direct your writing, if it's something that seems challenging to come up with right now, then it's not a huge deal if you don't have one! I'm sure that goals will naturally come as you continue to develop Luke's character through writing his small goals and specific threads that cause character development. However, if you are looking specifically for some inspiration for very long term, I would suggest consulting the Adult System which lists all of the potential careers that your character can pursue once graduated from Hogwarts. There's also plenty of systems built into the site regarding sports (Broom Racing, Quidditch, and Duelling) so this could help as well. My biggest advice though is to just write your character; in my experience Amadea's dreams have become more clear as I've just fleshed out her character by writing in threads. Hope this helps!

Thanks to both of you, I'll send that owl soon! By the way, Amadea, I love that little description of yours at the bottom.