well, i think the most important thing is just taking things one step at a time. sometimes it's a lot harder to go about terraforming and rearranging when you don't have a solid plan in mind (for example, i'm doing piece by piece of redecorating, and it's taking me quite a bit of time, and i need to put in a lot of work to make everything smoothly go into each other. had i planned it out beforehand though, i'd be in a much smoother sail for redoing my island).
bugs, fish & diving creatures, and shells are all really good ways to actively get bells on a regular basis. selling your bugs to flick, or your fish to CJ, when they come to visit is also a really good way to make extra money (but sometimes holding onto those bugs and fish is another tedious process). all you need to dive is a bathing suit; you can purchase one from your nook cranny shop.