1 - Base Rate of Fire
Both are fine, especially since they changed the values for S3, but rate of fire just makes spraying someone a lot easier overall, it feels a lot better,
if you are the type of player that ALWAYS use turret, which I do not recommend, Base Damage is usable, again I DO NOT RECOMMEND.
2 - Light Regen Shield
Nothing to say here, Light Regen Shield is just that good, never buy Heavy Shield on anything unless you have a really good reason to do so, Light is busted as always and Season 3 only made it better.
Note : if you lost round 1 or died and can't buy shield, ALWAYS sell blue for Light shield, and then come back for blue later.
3 - Passive(Royal Shield) Max Shield
Shield recovers so fast that Shield Recovery +100% upgrade is kinda useless whereas +30 Passive Shield HP can let you tank 1 or 2 more AR shots, which is a massive difference in some fights, this buy will also allow you to get your Awaken 3, biggest power spike for Audrey
4 - Stringified Damage
As much as the Headshot Damage VS Stringified Damage yap battle continues, I am a big Stringified upgrade guy, it makes a lot of the fights easier as it helps at countering stalling with paper, wall flutters, etc, both upgrades are fine, the higher elo you go, the more Stringified damage gets value.
5 and 6 - Spread Control and Active(Guns Blazing) Max Shield
At that point, buy order becomes a bit more straightforward, its important to get Stringified Damage before yellows for that extra oompf in fire power but after that you just want to buy whats left on your upgrade menu, I recommend both Active Max Shield and Spread Control, Overheat Rate really doesn't mean much compared to +90 Hitpoint on Active Shield and Recoil control is honestly completely useless after what they did to recoil patterns across every character.
7 - Stringified Movement SPD
I buy Stringified Movement SPD very late into my upgrades, and some could argue that you should buy it earlier, its up to feeling, I don't mind taking more time for rotates, depending on comps and scenarios I might buy it earlier, again, feel the situation, especially against rotate heavy team comps where you always want to be here to setup before an enemy execute.
8 - Handling Speed Increased
Let's be real, both upgrades are useless, but sprint is the most useless of the 2, just take Handling Speed man its not that deep.