Here are my toribash grooming tips-
I've had long straight hair for most of my life, I find that I can just use some texturizing matte paste and mess it up to add some volume so it doesn't lie completely flat and smooth. I use a medium hold one which tends to last throughout the day with no problem, unless I'm exercising but who cares how you look when you're working out. That's just what works for me though, there are many options to optimize for your specific hair type-
Pastes are pretty thick and give your hair a firm hold, there's a type for all hairstyles and it's my personal favorite. There's a few different types that give you a more matte to shiny finish. They're water-based so they're nice and easy to wash out. Hair clay is similar, but it's of course clay based so it expands in contact with moisture and makes your hair look THICK, while also being good for moisturizing.
Creams don't hold your hair in place like a gel or hairspray, but they make thick hair easier to manage, as well as moisturizing it and adding some volume. I get pretty good results with this if I want my hair to be neater and less messy than with paste.
Gels come in varying thicknesses, the thinner ones are good for light texture whereas thick gel will hold your hair in place very firmly, while also risking making it crispy as fuck.
Powder is nice if you get oily hair (it absorbs moisture from your hair), it adds some light texture and gives a matte finish.
Sea salt spray can be good if you're going for a messier, naturally windswept look, like you spent a day at the beach, but the effect is more subtle on people who don't have wavy hair. There's also the regular hairsprays but I've never been a fan of them.
Foams are applied to damp hair before it's dried, and can add some volume to longer hair, if you pick a high quality one.
Another thing to consider is how often you wash your hair; washing it too often will usually lead to greasy hair, just as much as not washing it enough. The products you use, or don't use, for washing your hair as it gets longer are also going to contribute to how it sits on your head, so that's good to consider. You can get products like volumizing shampoo and conditioner to help your hair sit how you want it to; washing is part of the styling process too.
For recommendations on products you should use or avoid for your longer hair, it's helpful to consult with a hairdresser so that you don't end up wasting money on trial and error. If they're a pro, they'll be able to tell you what type of hair you have, and what products will treat it well. They might be sponsored and trying to promote a specific brand or an in-house product but the insight is still valuable, you don't have to buy their shit