I wouldn’t recommend using DM groups, they don’t work the way they used to.
All you get is the comments so you look more legit, but in terms of reach they don’t help that much anymore…
If your clients have the budget I would recommend other options. Either m/s for very targeted and huge growth or storyviewing…
The best way to have an efficient engagement group is to get in touch with people in the right niche, active daily, and to build the engagement group yourself. It’ll be smaller than engagement groups you can find on huge Facebook groups (just type “Instagram Engagement Group” in the search bar on Facebook if you want to find them) but way more efficient.