What proxies I'll need?

most important thing with reddit is aged accounts which lurk.

Have accounts which just view pages a couple of times a day and don't post, upvoting on a new account looks artificial.

Reddit, as well as other social networks, can easily detect automatic tools and actions, so proxies are necessary in this case.
The recommendation ould be to use 1IP per 1 account, so if you want to manage 50 accounts you should have at least 50 IP addresses. Also, be careful - your accounts should be built, do some normal activity, be in various subreddits, etc. Otherwise, it would definitely look shady and you will be banned within minutes.
Don't use free proxies, buy them. It will be safer and your IPs won't be already flagged or banned. Don't use rotating proxies, it's better to have dedicated ones. Since not every provider have those, I would recommend looking into these:

1. Smartproxy - good price ($75 for the cheapest plan, so that's nice), high-quality services, you pay for the used traffic and not per IP so it's better in this case;
2. Highproxies - affordable and easy to use, so that's great;
3. Oxylabs - a bit expensive compared to others but nevertheless very valuable and fast proxies, lots of locations to choose so that could be a big plus.