LVL 1 Survival Insticts
because it lets you get free push and if you want to you can play further back with the increased duration though i generally sit behind the first fort close to lane. The extra health also guarantees you will push at a fast rate
Lvl 4 Adrenal Overload
More so that other builds you will always be using your symbiote and this is a huge buff espically when you get hivemind
Lvl 7 Needlespine
It prints free dmg and the increase range means you can snipe people to some extent
Lvl 10 Evolve Monstrosity
You aren't going to be paying attention to this the majority of the time, generally ult help it clear one wave, move it behind a few minions just so it doesn't take tower aggro then go back to team fighting. This is espically good on objective heavy maps that people don't pay attention to lanes like pirates where it can push uncontested I've gotten its AA over 300 dmg and it can kill heroes when needed
Lvl 13 Spatial Efficiency
With this you will be able to use your Q 4 times in a row, the 3 charges and the 1 charge that will get off cooldown by the time you use your other 3. Again great but still waiting for hivemind to make it better
Lvl 16 Volatile Mutation
Like I said earlier you are using your ult as a free lane push while you proceed to ignore it, the dmg helps clear minions signficantly so its just free push.
Lvl 20 Hivemind
The grand daddy of it all, while I would say abathur would work way better on a premade on VOIP so your teammates don't idiotically run around canceling the 2nd symbiote the 8q's you can dish out quickly at one target is huge amounts of dmg add that on top of 2 w's for wide spread aoe dmg and 2 shields (even thought he shield sucks but at least its something) and you got a lot going for you. If you are really lucky you will get 2 assassins who can really benefit from the attack speed boost like a raynor and valla.