biggest help is a better video card.
for even 40 bucks you could get any of several models of a 512m PCI video card that would be good enough for blockland.
more memory? even old computers have enough, and upgrading it anyways wouldnt really show much difference.
people are misled by how useful tons of memory is by stupid best buy commercials promising ram upgrades all the time.
more memory is great for multi tasking. but for simply running blockland on windows, your not going to need any kind of super computer ram count...
if your on vista and have 2g memory your fine as is.
xp, 1g is fine
play the game in full screen mode (try lower resolutions) instead of window mode.
i don't know if this is true for blockland, but as many other apps and games, windows usually gives priority memory to the active window. and when some games are put in window mode, the desktop still remains the active window instead of the game. this makes tons of slow.
lower draw distance all the way will help tons to