Sorry this is so long 😅
I have straight, fine hair and I currently use the Herbal Essences rose hip shampoo. It's really great at adding shine and making my hair smooth and soft (also smells yummy 😋). I've also used the Maui Moisture lightweight hydration shampoo (the pink bottle) and liked it.
Another thing that has been a game-changer for my hair is double shampooing! Because my hair is so straight and fine, it gets oily very quickly. I discovered double shampooing recently (which is just shampooing twice) and it gives my hair a little volume and it can last longer without looking greasy. I do every other day!
For conditioners/leave-ins I highly recommend anything with jojoba oil! My hair LOVES it and since I'm assuming we have similar hair types yours might love it too.
This is an add-on but the Tsubaki Fino hair mask is affordable and makes my hair sooooo shiny!