I have been playing online chess for more than a year now. I have been practicing tactical puzzles too. I have been delaying reading chess theory so that my tactical skills could improve. I don't know much openings.The only ones I usually play are King's gambit and Nimzo-Indian Defence for black. I don't know any theory behind these openings either. I want to improve my rating to atleast 2100. I think I am better in tactics than my game ratings suggest. For example, the Lichess tactics trainer rates me around 2020. I think I am not able to set up those beautiful tactical positions, but once they have been set up, I can spot tactics. Do I need to start reading opening theory, or do you think my tactical ability needs more improvement? I was thinking of starting by reading Irving Chernev's introductory book followed by Nimzowitsch's 'My System'.