What Jungler should i try and learn next?

Which stance is more effective depends more on what you're with than what you're against and also what you like to play imo. Phoenix is an aoe clear so it farms faster, while tiger is single target damage so it invades a little better, but depending on how you play both styles can do either one.

That said your damage will be more physical if you're tiger and more magic if you go phoenix. So if your team has all AP champs, then you probably should go tiger since the enemy will build MR against your team and you'll do more damage. If every lane is AD champs, then you probably want to go phoenix since the enemy will be stacking armor against your mostly AD team. Doesn't matter as much what you're against as what the enemy will be reacting to and how you want to play.

Most jungles won't out level the team, but out leveling the other jungle is pretty easy to do and that's what I was saying more so. You do that by either farming while they fail ganks (which is dependent on your team), or invading them and killing them or taking their farm so you're the only one getting exp (dependent on you, since if you get caught and killed by enemy lanes collapsing then they will be ahead in gold and exp and you will be behind).

ALWAYS try to get a leash to start your first clear. It isn't about if you can do it, it's about doing it faster. I generally start bot side since you'll get a stronger leash from bot lane (two champs to add damage) and that gets you clearing the rest faster, thus getting exp/levels/gold and just everything a little bit sooner.

Also if I get a leash for my first clear and you don't then I'll take less damage to start and have more potions so I can come fight you in you jungle w/ an HP advantage, or if we both go to gank the same lane before backing for first back I'll have the HP advantage and my team can possibly win the 3v3. Leash=good. Always try to get one.

Last thing is how early you can invade/1v1. Well it depends, you can invade w/ your team level 1 but that's a different thing and often not worth it bc it's risky w/ an unknown team against an unknown team. You may get hurt more often than you get helped. Otherwise the answer is after your first camp. I haven't played a ton of jungle since season 3, but I loved to counter jungle in those seasons and it was generally, clear buff (you started buff instead of small camp back then) and go straight to their buff at level 2 to steal it as nunu or kill them as mundo. (side note dr mundo is an awesome jungle, but w/ the current jungle doing so much damage on the first clear it's a bit dangerous in terms of your hp going pretty low unless you have spell vamp quints)

Generally though if you're aiming to kill the enemy jungle a lot, your goal (especially in low elo since it's easy and no one deals w/ being invaded well) should be to get good at killing the enemy jungle at level 2 or 3. Ideally you want to be able to kill the enemy jungle on their first clear 90% of the games you play in low elo (it gets harder the closer you and the enemies are in terms of skill level, but if you're significantly above the enemy in skill 90% is doable pretty easy). Killing them on first clear lets you at a minimum back with a hefty gold advantage, and 3 of the 4 buffs on the map. If you get really good you'll kill them take the buff and either have two or go get yours if you didn't, then buy and go kill them at their other buff/counter jungle and take their buff if they don't go to that side of the jungle (this takes warding in their jungle to know which to do bc you need to guess where they are and what they are doing and be right).

Tiger does single target damage so it can be easier to invade at an early level and kill them, but you can do it w/ phoenix pretty well too if you get to know the champ. My advice is play which ever stance you like better after you try both out and get a feel for which one suits you. You may decide you don't want to invade level 2, and instead want to clear the first clear super fast, get your buy before them, and then counter jungle, gank and push a wave in lane, clear your jungle again real fast (phoenix udyr clears fast so move speed quints can get you around a lot and aoe clear down a bunch of monsters for exp advantage). Then, only when you are up a level vs the enemy jungle (since you should have double the cs if you steal theirs clear yours and steal some lane creeps in exchange for a gank and damage on their opponent of course) do you invade and try to kill them w/ the level and item advantage from farming faster than them. It's all about finding the way to play something that you're most comfortable on and making it work. That's why trick2g makes "my way" videos. It's a way to play that works for him. Other people play stuff different and are effective. You just gotta find your style and play to that.