Probably the least intuitive thing that you should do to make your town look nice is buy everything from the Nooklings everyday. This will help you upgrade both their store, but more importantly the garden store. Bushes can look really nice placed around town and can be grown in rows (up to 12 bushes and trees can be grown touching) and you'll be able to buy cedar and normal saplings which make designing where trees go much easier. I recommend buying the saplings everyday, and buying the fertilizer everyday once it's available to try to get the golden axe and shovel. They let you cut down as many trees as you want or grow regular saplings using bags of money.
I actually hate the look of grass patterns, so I can't recommend using them - take the time to actually develop your town and put flowers. As everyone else though, I recommend placing paths. If you're going hardcore into designing this town, mapping it out on the computer to plan where you want everything helps (I attached a picture of what this looked like for my second town)
. This is really most/only important if you're planning areas that are going to be packed with buildings or public work projects (pwp). If you want the villager houses to all be in a line I recommend looking up plot reseting and the path method for plot reseting (essentially plot reseting + putting down paths so they are only able to move into specific spots). If you want to place specific pwps in your town, I recommend looking up the diving trick to get pwp pings. In both of these cases, it helps to have amiibo cards (either to be able to force move in and out villagers to get them into the right spot or to get villagers of the right personality into your town - though if you're attached to your current villagers that might not be the best idea).
If you want lots of flowers fast, Try going to the island and going on tours that don't involve pocket space, pick up all the flowers that you see while running around there and then bring them back to town! It's a very easy way to get more flowers (though you can't get violets of lilies this way I believe). Look up guides on flower breeding (and get ready for them all to say something different). Wealthy ordinance is best at first since it helps you upgrade your stores fast but beautiful town ordinance is a life saver once you have enough flowers - actually watering them everyday is a nightmare.
One last tip: if it's not too late, do NOT place down the campsite, reset centre, police station, or Roost until you are 100% sure you want them there. They're wonderful additions to a town, but they can ruin all your planning if you place them down and later change your mind for how you want your town to look since you'll never be able to pick them back up
Good luck! Your town is what you make of it and everyone will have different ideas for how they want their town to look. I hope you find a way to make yours nice that you like!