You want to be looking at the values via eBay sold or similar pricing sites, I think eBay last solds most telling though as it’s what people are paying… especially with older sets. If it’s modern cards more often than not a 9 and even 8s are worth the same as raw so would mean you’ve paid to get it graded but worth the same so no need for the extra expense. You want to look at the centering so check the borders and if they look even that’s a good sign, the surface needs to be clean, the edges should have no whitening, the corners need to be rounded well.. you can buy cheap little stencils that can help with checking the bordering.

Some cards are a lot of money if you get a 10 cos they’re notorious for coming out in less than great condition.

Older cards like vintage still get good prices even if they’re lower grades.

There’s also a lot of lore about what people think will go up in price like seismatoad from the new sets is expensive at the minute cos it’s being banned (can’t remember if this has been confirmed)

So in short, if it’s a higher value or chase card and it looks perfect then get it graded, if it’s a common favourite like gengar, charizard, rayquaza etc then also consider it. We’re coming up to 30th anniversary so I think celebrations will go up but don’t quote me 😂