Since I am currently working on the scarce data volume of one gigabyte per month (currently with a Fyve-card, because there was still credit on it), I try to handle the data as economically as possible.
Already some time ago I set up a corresponding setup on a vServer, which can be reached with a VPN connection and then takes over various tasks with a proxy chain. The whole thing runs under Debian and is probably easier to implement, but there has to be a little bit of fun. I will now briefly describe the path of the data from the Internet to my notebook, maybe this will serve as an inspiration for some people when they are facing a similar problem.
Station 1: Privoxy
So that advertising banners do not gnaw at the data volume, they are privoxy and an adblock filter list directly before the pages are processed further. This saves processing power in the next step, because everything that has been filtered out does not need to be further compressed (and in emergencies it allows surfing on the smartphone without ads).
Station 2: Ziproxy
As the name implies: ziproxy serves to compress and optimize the data. Mainly the images are reduced in size, but the HTML code can also be optimized (although the latter can cause web pages to stop working, so you have to pay attention to the configuration here and experiment a little with your favorite sites). Essentially, ziproxy does nothing else than to help the network operators with their Speed managersonly you can configure it yourself.
Station 3: Squid
To avoid the process of first removing advertising from pages and then compressing them too often, the result of steps 1 and 2 is cached via squid and delivered to the client. The squid address is entered in the client as http proxy.
The volume of data transmitted on the last route, which is realized via UMTS, is significantly reduced - which also increases the speed. Pictures look a bit less attractive due to the compression artifacts, but it is still better than surfing with GPRS throttling. The complete setup is of course a bit more complex to configure than described here, but the complete software (squid, privoxy and ziproxy) is available as Debian packages, which makes it much easier. For the VPN connection this tutorial is a useful start: PPTP VPN with the iPhone + Debian server.
Addendum: Run VPN server with Privoxy at home
If you don't want to operate the VPN server and the Privoxy/Ziproxy solution on the Internet and access your data at home at the same time, you can Raspberry Pi a VPN solution quite simple to configure. You will also need a router that supports a DynamicDNS server - otherwise you would have to look up the IP address of the DSL connection after each intrusion.