First of all, I don't care for nor want horse armor DLC. If you love stuff like alternate appearance to give some fancy clothes to your pardie, feel free to buy it. Also have to add that ME1 gives Bring Down the Sky for free and Pinnacle Station is not moneylaundry scheme but you can buy it with legit currency, so we're left with ME2 and ME3.
Assuming most of us want only missions DLC for ME2 and ME3 on PC (there are free or bundled DLC on consoles) and want to buy enough Bioware points for only mission DLC, the list is as appearing in Origin:
ME2:
Genesis - interactive comic book to make ME1 choices - they charge 320 BP for that crap?
Arrival - an assignment -
560 BP
Alternate appearance pack 2 - Miranda's butt never looked fancier - 160 BP
Lair of the Shadow Broker - a mission -
800 BP
Firepower pack - OP weapons - 160 BP
Aegis pack - OP aniper and 5 armor parts - 160 BP
Overlord pack - 4 assignments -
560 BP
Equalizer pack - OP armor set - 160 BP
Kasumi - 2 missions and a squadmate -
560 BP
Alternate appearance pack 1 - Garus' different looking butt, puhlease - 160 BP
ME3:
Alternate appearance pack 1 -
- 160 BP
Genesis 2 - make ME2 choices like you didn't play it ever - 320 BP
Leviathan - 10 missions of probably cut out content from the game -
800 BP
Citadel - 17 missions -
1200 BP
Groundside resistance pack - OP weapons - 160 BP
Omega - 5 missions -
1200 BP
Fireflight pack - OP weapons - 160 BP
From Ashes - essential and probably cut out mission/squadmate -
800 BP