FWIW,

I like the Bishop's Opening: it prevents the Petrov, it does not follow the "knights before bishops" maxim but is developing. It easily transposes into the Vienna, the Giuoco Piano, and the Two Knights. By allowing for a possible f2-f4 push (since you didn't yet play Nf3) it can even go into a King's Gambit. It often involves a d2-d3 to safeguard the e-pawn which is a quieter move that is sound and perhaps more to the novice's liking. There are not a lot of books on it and therefore may not be familiar to novice opponents. It does require a 1...e5 from black and so cannot be forced on 1...c5 obviously, but is a neat way to learn 1.e4 as a intro to the group of 1.e4 openings rather than just focusing on a single one like the GP. My .02 cent's worth.

For White- Scotch. For Black- probably Sczndinavian.

Marc Benford wrote on 06/25/23 at 22:50:12:


There is some discussion of two repertoire books with different approaches here that might be informative:
https://chessbookreviews.wordpress.com/2018/04/01/opening-lines/

We've had this or similar questions before at the forum. 
As I recall, opinion was loosely split between the followers of the late and much-missed Mark Morss (forum handle: Markovich), whose doctrine was that all novices should go through a phase of playing open games and gambits, to develop their tactical abilities and awareness of the importance of piece mobility, king safety, rapid development, the centre, open lines, forcing moves and the initiative.

A contrary opinion was basically that openings only matter in the sense that novices should just be taught a few opening basics such as controlling the centre, developing pieces and looking after the king. Practice and feedback from the trainer will then be sufficient to get them to a stage where teaching them some specific openings will be useful.

Another angle on this is that the trainer should first spend quite some time "letting them play" and gradually assessing the basic abilities of the students, since not everyone has the same talent for chess (or the same strength of mental "processor"). This might lead to a view that players assessed as clearly talented are likely to benefit from an extended period of the "Markovich doctrine" (as above), while clearly less talented players (e.g. who are struggling with basic tactics and calculation) need to be taught solid systems - that is if we want to keep them in the game and prevent them from becoming demoralised.
To express it another way: talented players probably benefit most from being given "spears"; less talented players need "shields".

Some ideas to consider:
a) Symmetrical play for the first move: 1.e4 e5, 1d4 d5, 1c4 c5, 1Nf3 Nf6
b) 1...e6

One book I can think of is "Openings for Ameuters". Its low theory lines and gives two system in some lines. It has also lectures and not only openings.

RosemarysBaby wrote on 06/26/23 at 16:10:16:


When the player becomes stronger, and is not a beginner anymore, he/she probably has developed a style and can start expanding/changing the repertoire accordingly.

I think it's a good idea to let them test stuff out at least occasionally, to give some feeling of discovery and really hammer down on the significance of imbalances. I wouldn't totally ban systems, just don't play them that much, long-term it'll get really predictable and boring+ since they often consist of a small set of position types, breaking out of that bubble can be difficult. 
Most people I think agree that e4 is most beginner-friendly due to the open lines and direct piece-play.

The Italian is good for getting a variety of position types and gives you the option to choose how sharp the game will be. The Scotch is good too though not as evergreen.

Against the Sicilian, I'd go open with 2.Nf3 and spam the English attack. The exception being 2...Nc6 where I'd recommend 3.Nc3 e5 4.Bc4 with an e4-e5 type game or 3...g6,e6,a6 etc. 4.d4 and back to the English setup. (This is just because Sveshnikov and Kalashnikov are very positionally distinct) Later on it'll be easy to start including more nuanced setups.

Playing black is a harder question, I'd second the Petrov and QGA recommendation, since they're much more positionally understandable than QGD, Slav, KID, Ruy, French etc. The problem with these lines is just that long-term you may end up less competent with complicated pawn play, so I'd say switch it up every now and then.

Ps. Can a beginner have a style? I don't think he/she/they can.