I wasn't aware that 1GB laptops were even made...that's...well...something else (to say the least).
Could you post the exact model number and your budget? Model number will help us know what kind of RAM you can put in your laptop (144-Pin SO-DIMM, 200-Pin DDR SO-DIMM, 200-Pin DDR2 SO-DIMM, or 204-Pin DDR3 SO-DIMM). Your budget will help us help you choose the best RAM upgrade possible (2x2GB or even 2x4GB).
In my personal experience, 4GB of RAM is inadequate to run my laptop (http://us.gateway.com/gw/en/US/content/model/LX.WYY02.035). When checking how much RAM is actually free to use, I usually have few hundred MB available at most. At this moment running Avast (anti-virus) and Google Chrome with 5 tabs open, I have 170MB of free RAM. Well, too bad if I want to open Eclipse and develop my app more, huh? If your laptop supports it and you can drop $50-$60 USD, I would pick up one of the below options:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231294
http://www.newegg.com/Product/Product.aspx?Item=N82E16820233081
Obviously if you can find them somewhere else reliable for cheaper, do that.