Welcome to the site! :) There is a lot of good info here that can help you on your way. I will give you some tips I have learned and I am sure others will lend theirs as well.
eBay and Craigslist is the best place to find lava lamps. New China lamps have a "murky" past and somewhat "cloudy" present. The China lamps all seem to be cloudy and have flow problems. If you are lucky, you can find one that is not cloudy. Either way, you can contact Lava World/Lite/Haggerty/Etc and they can send you a new globe. They will ask for pictures of your current on. If you don't want to do that, you can filter your lamp through a PUR water filter and it will clear up the cloudiness. I have done this myself and it works perfectly at clearing it up.