How much elo should I be gaining per day?


I am wondering how much elo I should be gaining per day, my elo right now is 861 and I am trying to get to 1000-1200 soon.
Even if you are improving at chess, variance exists and human players are inconsistent (sometimes we play well and other times we make mistakes; no one is perfect), so there is no linear path. There will be MANY ups and downs in rating and this is normal and expected.
Be happy with ANY progress (especially if long-term and not just short-term fluctuations) and keep the emphasis on learning and improving, rather than on rating numbers.
Here is a blog post on opening principles to help you reach your rating goals: https://www.chess.com/blog/KeSetoKaiba/opening-principles-again

Agreed with KeSetoKaiba, chess improvement is not measured in rating gain per day. Also the higher you climb the harder it is to get better. To get to 1000-1200 the main thing you'll need is the board vision to avoid one to two move blunders and to punish your opponents' one to two move blunders.
I am wondering how much elo I should be gaining per day, my elo right now is 861 and I am trying to get to 1000-1200 soon.