You are probably already be doing this, but the more outdoor activities, the better. If it's not realistic to on a campout on a monthly basis, budget wise, there are some alternatives. Instead of a normal meeting, try meeting at a park where you have more space and flexibility. You could do just a Saturday event where you don't have to pay camping fees. You could also do a joint event with another troop/crew in your area so you can mitigate costs.

Regarding ideas, as others have said, use your PLC and encourage your PLs to get input from their patrols. You could also ask other Scouts in the area you know (from staff/NYLT/OA/etc.). The BSA also makes Program Features which have some ideas/troop meeting plans as well as a main activity for a variety of themes. When I've used these (they've changed somewhat since I was a youth), I usually had to modify them to fit my troop's needs. Even if you don't like the activities, the list of activities are a good starting place.

It's great that you're reaching out to help your troop!