https://www.channelfireball.com/articles/a-different-take-on-team-constructed-pauper-instead-of-legacy/
http://www.daltenda.com/report-winner-paupergeddon-roma-pedro-iannello-con-affinity/
http://www.daltenda.com/affinity-pauper-2017/

3 Electrickery comes in against Elves, Goblins, and other decks with many 1-toughness creatures.
3 Krark-Clan Shaman - particularly for Stompy but also RDW and Elves. if you haven't used this guy before, make sure you hold ctrl until you've sacced the correct number of artifacts.
3 Metallic Rebuke/Hydroblast (can answer Gorilla Shaman before he hits the battlefield) and Pyroblast are great against things that are Red or Blue, the two most popular colors in Pauper.
4 Ancient Grudge is almost unbeatable in the Pauper mirror and has utility against other artifact-based decks as well. Natural State / Gorilla Shaman
2 Multani's Decree/Serene Heart - good option against Bogles but Ray of Revelation is fine, especially if you are worried about Pestilence. Also Tranquility
1 Feed the Clan - great against Burn (and Burn only, don't ever bring this in against RDW/Stompy, it's very, very bad.) I run a one-of. some lists also run [[Armadillo Cloak]] as a more general anti-aggro/burn card.
2 Relic of Progenitus (Tron, UB decks, anything that wants to do lategame

Journey to Nowhere is for matchups where you need more removal or want removal for creatures that Galvanic Blast can't kill, such as Gurmag Angler.
Armadillo Cloak is useful against the myriad of aggressive decks in the format. Making a 6/6 trampling lifelinker can put almost any game out of reach.

AGAINST:
Don't be afraid to use removal on a Germ token in response to Springleaf Drum. Messing up Affinity's colored mana can slow them way down when it comes to deploying threats from their hand.
Annul, Ancient Grudge, Gleeful Sabotage, Dust to Dust, Gorilla Shaman are all good cards against Affinity. Don't join a league without something for Affinity in your sideboard. The exception is Mono Black, where you have nothing to board in, but your matchup versus Affinity is already pretty good.
Kill Atog on sight. Do not let your opponent untap. The entire combo with Fling is instant speed and can be fired off in response to removal.
Letting yourself fall to four life or less means you die to a single Galvanic Blast. If at all possible, stay at five or higher.

https://www.channelfireball.com/articles/deck-of-the-day-affinity-pauper/
http://www.daltenda.com/report-finale-gg-pauper-tournament-by-roberto-francini/
https://www.mtggoldfish.com/articles/playing-pauper-affinity

https://www.reddit.com/r/Pauper/comments/6ffwvs/affinity_sideboard_options/
http://mtgtop8.com/compare?l=_311339_311423_310681_310525_310400_310626_310301_310291_310297_309939_309415_309889_309258_308863_308301_308218_308223_307526_307414_306490_306497_306417_306025_305671_305650_

http://www.gatheringmagic.com/alexullman-01242017-a-pauper-primer-aggro/
http://www.gatheringmagic.com/alexullman-12272016-the-pauper-8-from-2016/
http://www.gatheringmagic.com/alexullman-11152016-life-after-drake/
http://puremtgo.com/articles/arctic-pauper-show-%E2%80%93-affinity-20

http://www.castingcommons.com/optimal-primers/affinity/
http://www.mtgsalvation.com/forums/the-game/magic-online-formats/pauper/established/189712-primer-affinity
http://www.metagame.it/articoli-pauper/1149-deck-analisi-affinity-in-primer.html
http://www.gatheringmagic.com/alexullman-021616-pulse-of-pauper/

http://blog.daltenda.com/affinity-pauper/
http://www.mtggoldfish.com/articles/playing-pauper-affinity
http://www.mtggoldfish.com/articles/pennywise-pauper-affinity
http://puremtgo.com/articles/league-play-playing-affinity-pauper
https://www.youtube.com/watch?v=Gqk67DsshRI