How many phases for your Tournament?
Depending on your personal preferences, the number of participants, the game specific needs and the time / logistics constraints, there are many ways to pick a competition structure.
Nowadays, most tournaments are split into several phases, with early ones eliminating or seeding participants for the final main event.
Toornament allows you to create your stages, and organize them the way you want, meaning you can have as many stages as you see fit for your tournament.
But how many stages do you really need for your competition?
The League structure is a common single-stage competition : each participant plays each opponent (once or twice depending on the Robin style), and the winner is the participant with the most points at the end of the matches. Tiebreakers are often needed.
The other notable example is the ever popular Bracket structure, with its Double-Elimination version gaining more and more ground.
The single phase structure is very simple to understand for the participants and the audience, and is pretty easy to run for the organizers. All participants enter the tournament together, and one will emerge victorious.
Competitions with two phases are most of the time a "Group Stage + Playoffs" structure, where participants start the competition split into several groups, and only a fraction of them will qualify through the groups to reach the playoffs and compete in the final Bracket. Groups can be Round-Robin or Bracket themselves (See the different Structures available).
The two phases structures offers a good balance between the amount of matches played, the fairness for all participants and the hype brought by the final matches.
Three phases (and more!)
If you want a more accurate tournament when it comes to skill, you may want to have stages with a single purpose: seeding your participants. So for example, an early Swiss System, to seed your participants, then depending on their results, they're fed into the Groups, before going into the Elimination Bracket...
But you may also want to stick to a well-known format, just play more matches, like in the GSL competitions...
And because there is no limit, you can have a competition with over 10 stages if you want to, and only a few participants eliminated after each stage.
Another case would be several Qualifiers played in parallel, meaning the main competition might only be composed of 2 phases, but your tournament will have many more stages total, with the early qualifiers.
Possibilities are endless, but no need to say that the more matches are played, the more time you'll need to see your competition through, with everything that comes along.