I watch a lot of British television on BritBox and it’s inexpensive - $8.47/month.
I also watch a lot of free movies on tubi. Crackle as well.
The Roku channel has a lot of free movies as well.
If you have Amazon Prime they have a lot of movies as well.
Classic Movies+ has a few good movies.
I have at times subscribed to History Vault and the Smithsonian Channel.
If you’re a sports fan of a non-Power5 conference team ESPN+ has a lot games for those teams for about $10/month. The camera work and commentary is usually not as good as the main networks, but it’s worth the money. It allows me to watch all of my team’s away games (I go to home games.).
Mainly, just go online to the Roku website and browse through the huge selection and try some. Probably most are free. You can delete them later if you don’t like them.
One thing about movies though: it’s amazing how many movies are available and how few have any appeal to me. I have to search and search and search.
ON ROKU, there is a SEARCH option. So, if you type in a TV Show or Movie, ROKU will find all channels or Apps that carry that show, and whether it’s free or not. If you haven’t installed the relevant App, it will automatically install it for you.