Congrats on the Diamond II rewards!
My basic description of Splinterlands is a genuinely fun digital TCG where you can earn assets with real value just by playing. I think most people's interest is piqued by the monetary aspect, so it's easiest to get their attention by telling them what my account is worth versus what I initially invested, but honestly I'd rather talk about the strategy and deckbuilding. That's harder to do effectively without actually demonstrating it for them though.