Just Overdrive Afterburn first. That's all that really matters. The cooldown on it goes from a 16 second cooldown at rank 4 to a 10 second cooldown at level 5 (overdrive), and it's honestly the best ability that Glaive has.
The choice between Twisted Stroke and Bloodsong is up to you. However, I prefer maxing Twisted Stroke for the general help it provides to your damage (+25% Crit Chance, +65% Cleave Damage). Bloodsong can deal a lot of damage, but it's hard to use it because the enemies have to be relatively close to you. Also, while it casts, you can probably do more damage just auto attacking.

GET A SWIFT SHOOTER FIRST! The first recommended item the game recommends is a weapon blade. However, your first clear will be much, much easier with a slight boost in attack speed. There is a reason why most junglers, except maybe Reim should start with it. Your I would actually suggest making your first purchase at the Jungle Shop after clearing the jungle once, then taking the front 2 camps (2 small ones and the front regen). This should give you enough gold for both boots AND a weapon blade.
I like to build first into a Tyrant's Monocle. Many like to build into an early Sorrowblade, and that's an ok option, but only if you can confidently say that you're winning the early game. Glaive is very strong in the early mid game. And Sorrowblade is a bit too expensive to build into with a mediocre early game. This is in part because you can't just focus on pure WP; Glaive is a hero that needs good amounts of Atk Speed as well, and I would invest into at least a Blazing Salvo before going for your tier 3 item. Now, if you get slaughtered in the early game, I would look into purchasing a Tension Bow first. It's a really cheap item that goes well with Glaive's bursty style.
Now, let's say things go just normally, and you buy your Tyrant's Monocle. By now you should've invested into at least a tier 2 defensive item, unless you're absolutely steamrolling your enemies and can just do whatever you want. The next offensive item should either be a Tornado Trigger or a Bonesaw. If the enemies aren't really paying attention, and haven't built any Armor, or are building Shield, build that Tornado Trigger. As you may have noticed, Glaive goes very well with Atk Speed and Crit Chance/Damage, and Tornado Trigger grants all 3 of those stats. If the enemies are intelligent and have built into any form of armor, go into the Bonesaw. Not only does it grant you the Atk speed, it shreds off your enemies armor per auto attack, and with the boosted Atk Speed, you should be dealing a lot of damage.
For defense, it's what you should normally do; counter the enemies build. If their main damage dealer is a WP carry, build defense; both Metal Jacket and Atlas Pauldron are good options, as your support is probably building an Atlas Pauldron as well. You should probably only build one defensive item; you're the carry, not the Support, who's supposed to soak up damage and provide utility. HOWEVER THAT DOESN'T MEAN YOU CAN NOT BUILD DEFENSE!!!!!!!!! I see this too often in lower-tier matches, and it's terrible. Just because you might be ahead a bit doesn't mean you can ignore the enemy team's damage. I've lost games horribly after a stomping in the early game because of the laner not building any defense. So, look at what they're building, and build reactively against it.

I'm not the best Glaive in the world, and probably will never be the best Glaive. However, I can tell you that there are a bunch of helpful tips that I wish I knew when I was starting to play Glaive (who, for reference, is the first hero I bought with my hard-earned Glory). Most of it revolves around your Afterburn, which, in my opinion, is almost brokenly good; as long as you use it properly. It's honestly the perfect ganking tool, and provides superb mobility, being one of very few abilities that can jump over walls without a target. Let's look at how to use it.

FOR GANKS
It's rather obvious; crouch in brush, preferably when the enemy laner has pushed the wave to your side and your laner is still healthy. Always be looking for opportunities. The knockback+stun means that the enemy laner doesn't have to be pushed in very far for you to get a good gank off. In addition, if you really want it, use your boots before or after activation to get in position for a nice knockback. A neat tip for ganking is that you can get in position for a knockback to your turret more easily if you aim ahead of the enemy laner; in other words, aim diagonally, so that you are in better position post-Afterburn.

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Now, using it in lane is the easy part; you have one direction that you want to knock your enemies into, so it's very simple. But in other cases, such as in the jungle, the way you use it is slightly different. Glaive lacks mobility other than his Afterburn, and it's very easy to knock the enemies in a bad direction where you cannot reach them. To prevent your enemies from getting too far from you, you want to position yourself in a way in which you can knock your enemies into a wall. This keeps them right in front of you, where you can hack at them with your gas-guzzling axe. It takes experience, and that's about it. You can kind of practice in Practice Mode by doing this to the jungle camps, but really, just play around with it, and you'll get used to it. I used to always knock my enemies in a poor direction where I can't chase them, and would fail to secure a kill with the enemy health bar at a few millimeters.
An advanced tip would be to Afterburn into a thick wall, so that you are more in control of your position when you knock the enemies back. If the enemies are in close proximity and headed at you, you could do this to not have to go blazing past them and try to get into a good position. It's a bit hard, but useful to know.

Thank you for sticking through the whole thing. I hope that this helps in your adventures through the Fold. Good luck!