If you know your boil off rate, you can take any five gallon recipe and "divide by 5" the other ingredients as a starting point. Some recipe software will scale recipes up/down auto-magically.
You'll want a jewelry scale (around $15 USD) to weigh salts (CaCl, CaS04) and hops. More ideas over in 1-Gallon Brewers UNITE!. It's a long topic, so initially, start in the year 2018 and read forward
I like to use Brewers Friend to scale recipes down to 1G. To me it’s pretty user friendly. Once the software scales the recipe, you can tweak things to match the gravity and IBUs of the original. I also bought a book of one gallon recipes by Brooklyn Brew Shop, although I haven’t tried any yet.
I started with one gallon batches. 2 partial mash kits before I started biab. First couple recipes I tried were from the booklet you can get from this site and they turned out pretty good, you could give it a look and see if anything catches your interest. The gentleman that runs it is from my town and there is a recipe from one of my favorite local breweries in it . 1 gallon beer recipes