you should first of all be able to buy workers with resources. Then be able to upgrade the workers(then their appearance changes) with resources. Make them move faster, build faster, etc.
Love that the appearance changes after every 2 or so upgrades. It's what makes the game a 5/5. It would be even cooler if there was an appearance change after each question. Also like on the last upgrade you building should change gold or something to stand out! lolz
You need to be able to trade in supplies. Like 10k sticks for 8k goo. And then even be able to trade with other users. There also needs to be another gift option where you not only send random amounts of supplies, but you type how much supplies and you can send whatever you want. Give them a tower, give them a free upgrade, give them supplies.
mushrooms need to hold more gold. and there needs to be another way to earn gold. Like some quests. however quests might be too late. How about every time you log in you pick 1 of 3 cards and they have 5, 10, or 20 gold that you can win daily. Something like that please.