My 2 two year old loves playing with Duplo and is fortunate that her grandparents stored a bucket of it all these years (decades really) in the hope that she would one day exist. Adding to that Duplo / Big Blocks has been my challenge. I realized that what she really needed was some kind of base plate to fix the blocks onto and I also wanted some additional pieces that would support imaginative play (and keep me amused as well as she cried ‘Mummy! Come!’ and I find myself pulled along to be her playmate.
Duplo, I discovered, is expensive. It also seems to get sold in big themed sets and even at Christmas it doesn’t really go down in price; also in the big sets often the majority of pieces are just blocks which you might not actually need. I turned instead to AliExpress. It’s possible to order big themed sets from them but you can also buy individual pieces – like deciding that you want x6 flowers and x3 tree-tops. It’s great way to spruce up your existing blocks and you can often get free international shipping.
It pays to check carefully – there’s a vast size difference between Lego and Duplo so make sure that you’re searching for Duplo / Big Blocks and message the seller if you’re in doubt. It can also work out cheaper to get mini sets, depending on what you’re looking for, like getting a large pig (with moving head) + feed trough + two flowers + two blocks for USD$3.60 (and free shipping). Individual sellers will often have items on sale and there are big sales through the year so you can always put stuff on a Watchlist if you want to wait for prices to come down even further.