You're generating a decent return on ad spend on your Google Shopping Ad Campaign and now you're wanting to know which bid strategy to use to scale your campaign up and produce more revenue.

The fact is, you can scale a campaign with most any bid strategy so long as there are more clicks to be had from your target keywords. Obviously, manual bid strategy would take more management work but it's still possible to scale with it.

Automated bid strategies are not the be all end all. Sometimes it makes more sense to go manual on the bid strategy as it gives you more control over the campaign and generate a higher ROAS.

It just depends on what you're seeing drive better performance. Since you can't run a Google Ad Experiment with a Shopping Ad campaign, you'll just have to test one at a time.

Once your campaign is generating a decent return on ad spend, you can increase sales by simply increasing your budget.

It's best do this slowly at first because you never know when the campaign will hit a performance slump. Generally I will slowly increase budget as the conversion data becomes more statistically significant. Even then, sometimes your campaign can experience a slump, in which case it might make sense to lower the budget back down until you're able to dial in the campaign to produce a profitable return on ad spend again.