This how i typically level my sentinels:
Lvl 1: Hammer of lorent, use vengeance until you get rive.
Lvl 1-15: Either keep using hammer of lorent or craft yourself a slightly better 2hander. Once you hit 15, get dream thorn. Spec your rive for void dmg on the left side of the tree.
Lvl 19: get darkstrides and continue using rive.
This setup will stay the same till you get your mastery. For your second skill specialisation, get multistrike and start speccing it for forge weapons generation i.e. Attack speed and the node that says “using forge strike at max armament stacks consumes all stacks to summon forge weapons”.
Once you get your mastery, unspec rive, spec forge strike for forge weapon dmg. i.e. the right side of the tree and any other nodes that say they affect forged weapons as well. However, depending on how much damage you have, you might want to wait for your 3rd skill slot before you do this as losing rive is a big dmg loss.
From here on you will be a hybrid summoner, doing dmg yourself and through your minions. Continue upgrading your gear since your forged weapons depend on it.
This will continue until you get manifest armour specced. At this point, you should at least have these 3: multistrike/forgestrike/manifest armour.
You now have 2 choices depending on your gear.
If you have good gear for your MA to excel, get shield throw as your fourth skill spec and start switching to a pure minion play style.
If you do not have good gear yet, keep the above 3 skills. Put points into paladin and unlock sigils to buff you and your forged weapon’s dmg, until you have decent gear for your MA to become the star of the show.
After you get your 5th skill specialisation, your skill bar should look like:
Multistrike-forgestrike-manifest armour-shield throw-sigils of hope (early game minion playstyle). This setup is mana intensive, make sure you get mana on multistrike use from sentinel’s tree and spec out of it when you’re transitioning out.
If you have farmed gear on another character, then you can switch to the endgame skill setup shown in the guide and get javelin as your 5th skill.