Increase a laptop wifi range

Hi all,
I live in a complex which provides me an awful internet connection. Each building has his own access point, but the nearest to me gets disconnected (would you say go down maybe? or inactive?) often, and comes back in a minute, which is quite annoying,because the other access points don't have a signal strong enough to let me use the internet confortably. I have a laptop, I was thinking about buying something to increase the range of this, for, at least getting the connection to the other buildings access points, which looks more stable,and even if not,to swith from one to another which works wouldn't be bad. If then I get maybe a faster, open connection, also better...
I was thinking about this, 802.11g Wireless USB 2.0 LAN Adapter High Gain Antenna - (eBay item 200145726236 end time Sep-23-07 12:41:19 PDT)
It's cheap, even though not the strongest, but also more compact than others.
Maybe (what do you think?) I could also upgrade the antenna, and R-SMA antenna look to be much cheaper then USB one. Even though the usb dongle has RP-SMA (what does this mean, compared to R-SMA?)
What do you think? Sorry for the newbie's questions...but I'm quite confused.
Any comment and suggestion would be greatly appreciated.
Dedalus