For somebody at your level I'd recommend to focus on tactics and general principles (in openings/middle game and endgames) first, before worrying about specific openings (which have very little effect compared to missing simple tactics etc). Also if you learn typical general motives/principles of openings (attacking a pawn chain, developing pieces....) first they will help a lot when studying a particular opening later.
If you do want to learn an opening, I would recommend to first find out what kind of player you are, particularly whether you prefer closed positional games or rather open tactical battles. This will influence the kind of opening you are happy with.
In a second step, I'd take a look at some master games played in different openings and see what kind of positions result from different openings and which of them you like best. Looking around moves 10-15 is usually a good indication for what you get out of the openings.
If you have decided on an opening I'd start with learning the main line to some reasonable depth. Make sure not only to memorize the moves by heart but also to understand why they are made and what the general idea behind this particular opening is. For this you probably need some external help such as books, a database and online resources (videos, streams where good players comment on their moves live,...).
Once you have a rough idea of how this opening works you can think of playing themed games with an opponent. This will be a lot more efficient if your opponent has a much higher level than you or at least knows this opening much better than you; as in that case he will be able to point out mistakes you do when practicing. BTW, on lichess there are also regularly themed tournaments where you start from a custom position (randomly playing black and white): https://en.lichess.org/tournament
In any case I'd see these themed games only as a supplement and a way to test yourself. If you want to be serious about chess, it will not replace studying with databases, books, annotated games, analyzing your games for mistakes etc. Another good way to study particularly if you reach a level of Elo 2000 or so, is to pick a GM who is playing your opening and to follow their games.