2questions:
for how many usd do i need to buy to receive significant stake?
is ldoge stakable on the web?
I'd start with at least 1,000,000LDOGE ($82) - price is dirt cheap right now, if the price rises to 2 sat - you'll double your money. It'll likely rise when DOGE does next (but never guaranteed)
You'll need to download and run the wallet to stake
(EDIT - There is a risk on the coin as well - since you can't sell it immediately right now as price is 1 sat - so if you want to sell at 1, you have to join a queue of sell orders and wait a few days)
Oh, ah, I just checked on a few numbers, you can even get it a little cheaper than 1 Satoshi right now in the LTC or DOGE markets. 63% of a Litecoin ($45), or 30,000 Doge ($42-45) will net you 1 million, and like Starmman said, indeed if it goes up to 2 Satoshi you're looking at something in the range of $160 per $40-45 in.
If it goes up to two, you should've bought it now.... just sayin'.