MRdumful | 110 points
Encoded Link: aHR0cHM6Ly9tZWdhLm56LyNGIWt1d3owYUlLITN3eUoxWkNTQ2F6Q2VfeUpyeVQ3OWc=
Decode Link With: https://www.base64decode.org/
Disclaimer: This does not include Ultimate FF or All-New Ultimates because they do not seem either important or well regarded.
This link is an adaptation of this reading order: https://www.comicbookherald.com/the-complete-marvel-reading-order-guide/ultimate-marvel-universe-reading-order/
If there is anything that I should add/remove feel free to let me know.
update (January 11, 2018): Added "46 Spider-Men II"