Your best bet is probably to go to your local game store--they'll have a big pile of lands they use for sealed/draft events, and likely would sell you 20 for pretty cheap.
Otherwise, you can find a lot of options by just searching around. A quick google search showed you can buy packs of 100 lands on Ebay for about $5.00. I am not super fond of using Ebay to purchase Magic cards, but, considering lands are not overly high value, I doubt you would have anyone counterfeiting them.
May 12, 2021 3:14 p.m.
I doubt you would have anyone counterfeiting them.
It takes like $1 to make a half-decent proxy that would pass a cursory inspection. That's WAY more than a basic land is worth. If you do find a proxied Mountain , it's honestly probably worth more than a legitimate one.
I seem to recall WotC actually selling land packs themselves, but that was a while back and I don't think they do it anymore. LGS is the way to go for sure.
May 12, 2021 3:50 p.m.
It's a it overkill but you'll never need to buy lands again land station
You could also buy a deck builder's toolkit or older fatpacks/bundles come with 20 of each land