can someone explain exploring.does explore number get smaller each time u explore? is there a time where explore becomes single digit returns thks

Click explore, then click help information on exploring. There's alot of those explaining different functions in game.

https://www.earthempires.com/alliance/help/out/explore

I noticed a limit on exploring at times (e.g. "You must build on existing land before exploring more". Is that only at early turns or is it always there? Basically wondering if I can still batch explore?

You must have at least half your land built before you can explore more.