The level of bidding should generally also depend on the respective product's current state.

That means being more defensive if you don't have any or few reviews, and more offensive if you want to push your organic keyword rankings.

Launch Phase (still very few reviews):

Automatic Ad Groups:

if acos < target - 5% after 100 clicks, increase bid by 10%

if acos > target + 2,5% after 100 clicks, decrease bid by 15%

if impressions < 500 after 7 days, increase bid by 10%

Manual Ad Groups:

if acos < target - 5% after 10 clicks, increase bid by 10%

if acos > target + 2,5% after 10 clicks, decrease bid by 15%

if impressions < 100 after 7 days, increase bid by 10%

Growth Phase (conquer organic rankings):

Automatic Ad Groups:

if acos < be-acos - 2,5% after 150 clicks, increase bid by 20%

if acos > be-acos + 5% after 150 clicks, decrease bid by 20%

if impressions < 500 after 7 days, increase bid by 20%

Manual Ad Groups:

if acos < be-acos - 2,5% after 1X clicks, increase bid by 20%

if acos > be-acos + 5% after 1,5X clicks, decrease bid by 20%

if impressions < 100 after 7 days, increase bid by 20%

Established Phase:

Automatic Ad Groups:

if acos < target - 5% after 200 clicks, increase bid by 20%

if acos > target + 2,5% after 200 clicks, decrease bid by 20%

Manual Ad Groups:

if acos < target - 5% after 2x clicks, increase bid by 15%

if acos > target + 2,5% after 2x clicks, decrease bid by 15%**Going out of stock Phase:**

Any defensive rule-set, but sellers will typically just want to turn off the product's ad groups completely in this phase.

Push (back) Phase:

Automatic Ad Groups:

if acos < be-acos - 2,5% after 150 clicks, increase bid by 20%

if acos > be-acos + 5% after 150 clicks, decrease bid by 20%

if impressions < 500 after 7 days, increase bid by 30%

Manual Ad Groups:

if acos < be-acos - 2,5% after 1X clicks, increase bid by 30%

if acos > be-acos + 5% after 2X clicks, decrease bid by 20%

if impressions < 200 after 7 days, increase bid by 30%

This article (click here) explains how to determine the Target (and Break-Even) ACOS.

This article (click here) explains what 1/1,5/2X clicks means.

Disclaimer

Different condition values or actions may make sense for various products / niches. The above rule-sets only serve as inspiration.

Additionally, you may want to create even more rule-sets for campaigns with different types of goals.

For example being more defensive for your "keyword discovery" campaign (auto and/or broad) and more aggressive for your high performing Keywords campaign.