Hi, start with a raspberry pi along with squidproxy, there is plenty of info on the internet, when confronted to a roadblock, ask the question precisely to google you’ll get an answer.
Don’t listen too much to people telling you won’t make it if you have to ask (sorry dma0245, no offense), alone you won’t make it, but internet is a big place.
I did one proxy with a raspberry 3b+, a HUAWEI 4g dongle, squidproxy and webmin. It was few months ago and i remember i struggled quite a bit as the noob that i am. But i hanged for hours on internet to find solutions for the problems i encountered. At the end you find out that the pain comes from very small details that any fellow with experience would nail in few minutes. So tbh i don’t really understand why people asking for this kind of things here and other social marketing forums are often deterred to do so…
On the other end, if you think you gonna run 10 reposts accounts at 700 F/700 UF/700like and story views per day on a 50go dataplans, you gonna have a bad surprise.