The simple formula here is get the largest green that your budget allows. A larger green gives you more options and is more fun.
When it comes to a Supreme Green, you probably don’t want to go any smaller than 150m2. A green smaller than this will be too expensive for what you’re left with. Yes, a small green will still look fantastic, but it won’t give you too many playing options. It will just be too small.
My green is around 220-230m2. It’s still relatively small when you compare it to a normal sized putting green, but it’s large enough to practice 30 foot putts, and hit all sorts of shots to it. A smaller green isn’t large enough to allow the ball to stop and check. I put together a short video with more info. As usual, feel free to contact me with any questions.