Static holds should be trained after you have a good base strength. Many people get excited and want to do everything at once and end up injuring themselves or quitting. Make sure that you have the prerequisites for the static exercises.
Back lever: Prerequisite - Good shoulder mobility & flexibility, otherwise you're gonna injure yourself. Do Skin The Cat and German Hangs to get better shoulder mobility. As far for progressing, another prerequisite is lower back strength, so train lower back crunches + holds, lower back raises + holds, and then the progressions would be: Tuck Back Lever, Advanced Tuck Back Lever, One Leg Out Back Lever (you can also do this as reps, from tuck back lever, get one leg out, then the other and repeat), Straddle Back Lever, Half Lay Back Lever, Full Back Lever. There are many ways and more progressions like negatives, tuck outs, but for the actual holds, those are the progressive holds you should do. You might see people use a closer grip than shoulder width, it makes this exercise easier because of the leverage created with triceps-lats, and as you get the technique (muscle usage) part, start widening the grip. Make sure you have at least 5-15 seconds back lever before you start trying crazy stuff like one arm back lever. You should have protracted scapula and tension all around your body.
Front lever: Prerequisite - Good pulling strength (at least 10-15 strict form semi-slow pull ups), good core strength (when you're able to do dragonflies and dragon flag hold, you pretty much have the core strength). The holds are the same as the back lever: Tuck Front Lever, Advanced Tuck Front Lever, One Leg Out Front Lever, Straddle Front Lever, Half Lay Front Lever, Full Front Lever. Like I said there's other supportive exercises, like Front Lever (variations) Raises, Front Lever (variations) pull ups, Front lever negatives, but I am talking about the general holds. You should have a retracted scapula (or normal, but never protracted) and tension all around your body. This exercise is like 80% back & lats, and 20% core, although the core still plays a big part.
Planche: This one I can't do myself, it takes years to get. Prerequisite - insane shoulder strength, insane wrist flexibility & mobility, and a lot of core strength as well. Start with the tuck planche obviously, and if you can't even do that yet with good form, just skip it and focus on getting stronger shoulders (Pike push ups, dips, so on). Pretty much same progressions here as well, advanced tuck planche, one leg out planche (not sure if this is a thing), I think a better progression is Half-Straddle, then you go to straddle, and then the full one. Of course once again there are Negative Planches (from handstands), Planche (variations) push ups. In this exercise you want to have a protracted scapula, that's where a lot of people get it wrong and don't see results. And honestly it's very hard to even hold a protracted scapula even in the tuck planche let along the full one..
General advice about static holds:
Many people will say you need to hold each progression for 30-60 seconds before you go to a harder one, but that's ridiculous, because you're training for strength and not endurance, so I'd say 5-15 seconds should be fine before going to another progression. If you have fat, focus on losing it as it will make it 100 times easier, and that might actually be the reason why you can't do the full static holds, you might not have the strength for your current bodyweight, so another tip that helps in this case is using resistance bands if possible. And remember, even when you get the Full variations, you shouldn't neglect training the easier ones, especially the Skin The Cat & German Hangs for the Back Lever, if you stop you might injure your shoulder. OH. MAKE SURE YOU DO EACH HOLD OR PROGRESSION OF IT WITH STRAIGHT ARMS. THEY ARE STRAIGHT ARM EXERCISES.
Even though I said lose weight to make it easier, one thing that really sucks and I get angry at each person who does this: douchebags who are like 50-60kg and can do the static holds mock others who can't (generally even any calisthenics exercise really, not only the statics), and it really grinds my gears. I'd much rather see a guy who's heavyweight like Chris (and myself personally actually haha) do static holds, that's real strength.
Hope this was of any help, I know it's a long answer haha. Just search Google though, I probably missed something.