I think the Moscow and Rossolimo would suit you temperamentally, I play the Rossolimo, there's a bit to know but it's not super difficult to play and it's an interesting opening. That said, considering the Moscow and Rossolimo are quite different beasts and then you would need something against the e6 Sicilians as well, it's not a simple answer.
If you want a universal response to the Sicilian, I quite like the look of The New Anti-Sicilian, by IM Fernando Valenzuela and might give it a go myself sometime. Chessable have a 30-day money back guarantee, so you could buy it, have a browse through and see if you like it, and just return it if you don't. It is just getting you equal positions, but Black is very unlikely to have played them before (I play the Sicilian and I know the first like 4 moves against this and then have no clue) and there are plenty of ways for him to go wrong.
For the French I would really consider sticking with the Tarrasch. For the Closed Tarrasch with Nf6, I can recommend 1. e4 e6 2. d4 d5 3. Nd2 Nf6 4. e5 Nfd7 5. Bd3 c5 6. c3 Nc6 7. Qg4, theory is over at that point, in the Lichess database this move is played 0.4% of the time and it's not like the Tarrasch is common anyway, so there is no chance your opponents have ever seen this before. When I play this online my opponents blitz out the first 6 moves but Qg4 is invariably met with a long pause. If you spend 10 minutes messing around in Lichess Explorer in that position (you especially need to know what to do if your opponents hit you with h5 or f5) you will have much more of an idea of what is going on than your opponents do. For the Open Tarrasch (3...c5) I play 4. Ngf3 and I think getting to a decent position from here for White is easy. I am scoring well from that position and I am very hazy on the theory.
For the King's Gambit, I haven't played 1...e5 in a while but I used to play the Falkbeer Countergambit and was very happy with it. This results in equality at best for White. There's a video here on it that looks pretty good.
Hi,
I'm looking for suggestions on how to fill in the gaps in my opening repertoire, specifically against the Sicilian and French with White and against the King's Gambit with Black.
Quick background: I have an OTB rating of around 1500, and I frequently play classical OTB games against much stronger opponents (sometimes up to 1900). Combined with the fact that, as an adult improver, I'm not exactly great at fast calculation, I enjoy playing very classical and very solid openings (Scotch Four Knights with White, Petrov and QGD Semi-Tarrasch with Black). I'm struggling a bit to find similar variations against the openings mentioned above.
Sicilian:
I currently play a simplified version of the Open Sicilian, and while my results are reasonable, I don't feel confident against some setups, e.g.,