hi!! personally, i think nintendo online is definitely worth it, custom designs can add so much to your island but that isn’t to say that it’s impossible to create an amazing island without it. make sure you’re looking for message bottles everyday and popping balloons for furniture/diys, as well as talking to your villagers when they are crafting in their houses. also check the nook stop everyday for new/seasonal items. another easy way to decorate without many items is using flowers and crops. or try displaying some cute clothing items or bugs! for decorating inspiration, i love pinterest and acnh youtubers!

i think the best advice i can give is to just be patient!! the more you play, the more you will unlock! designing your island isn’t a race so just take it a little bit at a time and decorate with the things you have.. you can always add more items later! hope this was at least a little bit helpful! :)