I would say Arch if you are that tight on resources and comfortable doing so (the setup isn't as bad as people make it sound, just look up a guide online), but Endeavour would get you to more or less the same place with much less complexity.

That said, is there any chance of upgrading the RAM? an extra 4GB or 8GB stick of DDR3/DDR3L off ebay would not cost too much, and would make a world of difference for things like modern web browsers.