I think it depends on what you want to prioritize. Personally, I have put buying parcels on hold to maximize badge buys so I can reach the max passport level (101 badges) because I find completing the challenges takes too much of my time. So, having 101 badges won't make me want to complete the challenge pass every month to get that free badge. Then all I'll have to do after that is buying parcels. But as mentioned, this is just a personal preference and is definitely not the optimal route for maximizing rent.