How do I maintain volume at the temples? ㅠㅠ Also, please recommend a good value hairspray!

Maybe because my hair is thick and heavy, even when I add volume, it collapses and goes flat quickly.

I'm not sure if I'm doing it wrong. I use a flat iron to curl the inner layer of my side hair and then cover it up with the hair on top. Is there a better way to do this? Also, are there any good, affordable hairsprays for holding my bangs in place? I really don't like it getting greasy.