I would vote to put $1000 in there to buy some land. I believe the thinking you spelled out in this post is sound.

It will likely turn into a good long term investment. The odds are that this land will appreciate at a minimum of 20% per year which is SPInvest's baseline.

If the game continues to grow at a nice rate or has a big breakthrough, then it could end up providing an enormous return.

Since I am not into Splinterlands either, I am not sure how the land is tied to the game but as long as someone knows, I think this a valid idea.