It might be worth it to buy the planks with gems (depending on how many you need of of course) because the higher up you get in the game, you need way more nails than planks and will cringe knowing you've deleted all those nails. Either way you look at it, it stinks. We shouldn't have to use gems for materials nor should we have to be delete ones that we actually do get just to make room. This is a huge problem.
As for me, there's nothing more irrating than leveling up to a new feature in the game (atm for me it's the Seafood Shop) just to find out you need more expansions before you can even build it which to get enough parts for both, will take months