I personally prefer 2.5 gallon tanks, and so do a lot of members here, but I think a 1 gallon is fine so long as you're willing to change the water regularly. I know, some members here have become a bit...aggressive with the way they post, it's a bit odd to me since the forum used to seem a lot more inviting.
@OP: Welcome to the forum! He's a nice betta. The fact that he's laying around and 'itching' himself on the gravel does worry me a bit though.
Puck (Yellow koi HM king) / Scar (White HM) / Salt 'n Pepper (Silver HMPK) / 'That fish' (Copper butterfly HM) / No name (White DT) / No name 2 (Turquoise/white marble HM) / No name 3 (Lilac HM)
Bo Peep (Cambodian VT) / Goldilocks (Yellow VT) / Joie de Vivre (Multicolour VT) / Lil' Peep (Blue VT) / No name (Dalmatian VT) / No name 2