Picking openings based on simplicity of ideas, regardless of theory?

This is quite the wall of text, so tldr is at the bottom. Anyways,...

Often I see people mention that as a beginner you shouldn't play openings that are dense in theory. While I agree, it seems to me that theory doesn't matter that much at this level anyways. Even if you know only 4-5 moves of  a couple of common lines in an opening, you'll most likely be out of theory by the time you reach them, because your opponent 9 times out of 10 won't know more anyways.

Should you then instead focus perhaps on playing openings that have clear, simple, concise ideas and plans behind them, regardless of the amount of theory? Or is it the case that, with the amount of theory, the complexity of ideas also grows?

Any example of openings with clear and consise ideas would be appreciated, regardless of the amount of theory. I quite enjoy studying it to be honest, it takes my mind off of things that stress me out like work deadlines, etc.

Thing is, lately I've noticed I much rather play with black because then the ball is in whites court to pick an opening and I just react to it. Sometimes with "theory" I've looked at for a specific opening, sometimes just trying to play in line with basic chess principles. Thus I'm looking to study an opening for white, not in depth, but enough to have a clear idea going into the game and later I can expand on the theory.

As a disclaimer, I'm aware that beginners shouldn't study openings in depth, since there are more important things to learn first like tactics and simple middlegame / endgame ideas and if you look at my games, I'm sure you'll find many instances where glaring deficiencies in these areas can be identified, however for some reason the frustration of not having a plan going into the game as white makes chess very unejoyable, which I would like to solve.

TL;DR: Any examples of openings with clear, concise, 'simple' ideas and plans would be greatly appreciated, regardless of the amount of theory.

The problem is that every opening (also difficult stuff like Kings Indian or Sicilian) has an "simple idea" with logic behind it. But that doesnt mean that any opening is simple. Openings with almost no theory are usually sketchy and not too good. I would try the Queens Gambit, the French and the Queens Gambit Declined. The setups are quite "simple".

Oh I agree, perhaps 'simple' is the wrong word to describe this. What I had in mind is, for example, something like the 150 attack against Pirc. While I wouldn't say it's simple, you have quite a straightfoward and clear idea of what you want to accomplish after the first couple of moves and you can build on top of that.

Thats a good point. But in a calm setup like the London i have also a quit 'straightforward idea' of how i want my position to look even though its not that aggressive in terms of checkmating (Bishop to f4, pwans to c3/e3, castle, and after development often a4 to push a5/a6 later and create weaknesses and play on the queenside, maybe c4 to combine these plans and Rook c1 if the c4 file opens up.

Thanks for the suggestion, will look at the London. I did play it a bit when I started out with chess and I somehow didn't like how the game played out of the opening so I steered clear from it. But it's been some time, so it's surely worth giving it a second look.

You might be interested in My First Chess Opening Repertoire for White by Vincent Moret (I think he wrote one for black to). His selection is based on a clear overall plan. I agree, if you know the plan or key themes for the opening, you can continue to develop along those lines even after it has gone off book. It helps unify moves around a central idea. I find it a far more satisfying way to play.

London system, lol. https://lichess.org/study/KjivNw7F

I'd recommend the Italian game. Really simple, develops pieces quick, and not that much theory behind it either.

There are different types of simplicity.

One type is that you can get a similar setup over and over, without having to adjust your plan very much to what your opponent is doing. The is part of the appeal of openings like the London, KIA, Catalan, KID.

Another, I would say more important, is understanding the basic attacking ideas when transitioning from the opening to the middle game. There are some openings like the Catalan that are clearly rock solid, but I don't yet understand the attacking threats they should be making.

Ruy Lopez and the Italian game are examples of openings, where there is in principle a lot of theory, but which are quite easy to play with natural moves. Both openings develop pieces in a natural way and it is possible to castle early. Ruy Lopez is perhaps even more flexible allowing slow and solid development (lines with d3, this is not a bad line, Carlsen plays it regularly) or a quicker fight for the center (0-0 and d4 without d3 in between).

In both openings there are a couple of themes you should know. In the Ruy Lopez some of them are how to regain the pawn if you play for instance 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. 0-0 Nxe4 (the open Ruy Lopez) or the standard knight manouver Nb1-d2-f1-e3/g3 and perhaps to f5. In the Italian (I don't play it as White) you need to know the theory of the Evans gambit or Fried Liver precisely if you play them, if you choose a less sharp approach, you need to be aware of Black playing d5 as it hits the bishop.

While there is a lot of theory, I've played about 100 games in Ruy Lopez as White and I've never reached the branching point of the main line of the closed Ruy Lopez (where the actual theory starts) and only once the queen exchange of the Berlin variation. Instead quite common variations seem to be the Steinitz one (... d6, self-pins the knight) and Bc5-lines (Cordel/Neo-Arkhangelsk/...).

If you know the theory, you should know how to play against the move that doesn't belong to the theory and take the advantage of it. For example, the Grünfeld (I don't recommend playing it if you're not an advance player) exchange variation is pretty dense in theory, you can easily take advantage of bad move if you understand the opening. I played it and people under mid 1700 usually play the wrong move and gave me serious advantage.