We all had to start somewhere
1. A proxy host is the best to have, normal hosting doesn't usually allow proxies. There are quite a few but Vectro's xproxyhost is the best value for price and bandwidth. The server config is something the host can worry about unless you have your own vps/dedi setup, but a fast server with lots of ram helps.
2. Glype is the best script to use, it has plugins to make sites work properly (YouTube, Facebook etc.) and there's a wide variety of themes to choose from but some are better than others for earnings. The underground theme usually does well, it's not pretty but has good ctr. Phproxy script is still used but doesn't work well for popular sites and is no longer supported. There are others too but nothing beats Glype imho.
3. Pitfalls, mmm, there's the abuse issue of course like spammers using it to send emails and post on forums, or bots that use it for similar, and sooner or later filtering software will block it reducing traffic.
4. You've covered the worst countries although Russia will cause problems sometimes, it's worth blocking them too. Personally I block countries with little ad revenue as well, which is most non western countries, it makes the hosting resources go a lot further so you're not giving away the service for free to those that make nothing for you in return. The actual blocking can be done with the proxy host, most have the mod_geoip installed so it's just a few lines in the .htaccess file. If you have your own vps/dedi then the easiest way I've found is edit the script index file but you can install the mod_geoip if your technically minded and understand unix/linux (I don't).
If you just want to try it then start small at first and build on it and learn as you go. It won't replace your day job anytime soon but it'll make some money usually. An adsense account helps, other networks are pathetic compared to big G but only on the home/index page. You don't have to have ads on the proxy page and the choice is limited so you can put your own affiliate ad banners or your own sites until you get the traffic to apply to adversal unless you already have an account with them.
It's not hard to do though. Getting traffic is probably the hardest part, submitting to listing sites helps to get started as does email blasts but for longer term then seo works best but takes longer. Using .info domains is the cheapest way to start and they will work alright although .coms are better for 'branding' and long term income. To make any decent money though it's a numbers game, just keep making more, and more, until you have a network. Traffic will come and go, there's an initial surge after promoting then it'll drop off, then sometimes picks up again for no apparent reason.
If you want to do it for the absolute cheapest then get a .info domain or even a free .tk and use freeproxyhosting.net to get started. You'll lose little then and you can practice for next to nothing. The free domains aren't so widely accepted into lists though and are looked on as spammy so not the best imo, it's worth the few bucks for a 'proper' domain.