So, you want to try pauper, and your first question is what colour? This question is based off of personal taste, but the first thing to learn is that mana-bases are much harder without a half dozen dual lands that can enter untapped or fetches outside of evolving wilds. So, what are your options? Here are the top lands in pauper.
Fixers
So first, we have our fixing lands, and the first and formost fixing lands in pauper are the gain-lands.
So the gainlands are basically dual lands that enter tapped but give you one life. That basically all dual lands enter tapped is part of the reason pauper is played such a reasonable pace, and the incidentle lifegain matters more than you might realize, especially with the next set of fixers.
Called karoo lands thanks to the original Karoo, these lands enter tapped and bounce one of your own lands, but they produce both colours of mana. Even slower than most tap lands, this is offset by the card advantage of having 2 lands act as 3 as well as ramp potential for land untappers like voyaging satyr, and the bounce can be offset by using the mana before you bounce your land and then getting utility off of the land re-entering the battefield through lifegain or other effects. Be aware that too many of these can result in an opening hand that cannot be played courtesy of having only these lands which have no use without another land to bounce. Overall, be ok with a much slower deck that intends to use cards efficiently rather than quickly.
Almost strictly worse than the gainlands, essentially they can be copies 5-8. Sometimes the gate subtype can matter, mostly for searching effects as gatekreeper vine is a decent card for some decks, but mostly, don't play these unless you need to.
Onto search lands. Ash Barrens is probably the best of the searchlands because it can enter untapped for mana when you need it and fixes your mana to any type with any other land when you need another colour. The added bonus of being able to thin out your deck and getting a card in your bin is not irrelevant, either.
A staple card in limited that sees fringe play in standard, when you need more than two colours, this card gets you any one of them you need, and has a copy 5-8 with terramorphic expanse which is a functional reprint of this classic. Aside from fixing, you may put it into your deck because it thins out your deck or put a land in your bin for delving, or you can use it in a landfall deck to have a two trigger land. Not every deck wants this as it has the same slowness as the duals, but for some decks, this is exactley what they need.
Utility Lands
Probably the most infamous land cycle ever printed, having all three out at once let's you create seven mana for three lands. With expedition map legal as well as a large number of ways to search the top x cards of your library, this comes out often, and getting this much mana this early is insane enough that there are entire decks based around it. Unlike the other lands on this list, though, you won't be sticking these in non-tron decks, so worry more about stoneraining these than playing them.
These lands all ente tapped, but they produce standard colours and effects that can make the mana slowing worthwhile. Bojuka Bog is easily the most playable, as hating out graveyards is very powerful in a format with flashback allstars like Chainer's Edict and delve creatures like Gurmag Angler. Halimar Depths is cute, but often frustrating unless you have a way to shuffle your library as rearranging three lands doesn't help you draw what you need. Khalni Garden looks out of place at first, but its power comes in creating tokens to either slow aggro decks down or proving sac targets for saving your big creatures from edicts. In all these cases, the cost is generally minimal enough to allow for the effect.
Artifacts lands are a thing because affinity is a thing. For those who do not know, affinity is a mechanic that makes cards cheaper for each artifact you control. Add to this metalcraft and artifact sac cards, and these lands, which enter untapped and work for coloured mana, become staples in any artifact matters decks. Do be aware that these are hit by artifact destruction, so don't forget darksteel citadel as an indstructable variant.
Cycling lands are a quintessential low cost land that allows you to use them for mana early on and then cycle them for the cars you need late game. Coming into play tapped means you don't want them in every deck, but when you run a high land cou nt, these become great ways to control your curve.
While mana fixing may be a priority for some decks, others have all the fixing they need and have found that gaining two life keeps the aggro decks at bay. Also, with several ways to bounce your own lands to get cool effects, lands thaty gain you life and enter untapped become even better. Overall, great for control decks that need alot of lands and a way to stave of burn until they can get there counters up and running or get Evencar's Justice down (more on that deck at a later time.)
Whew.... that was alot. Don't worry, I intend to shorten these in the future, but lands are the foundation of your deck, and also one of the biggest differences between pauper and other formats in selection. So, thanks for reading, and I'll talk to you later.