The heat sink is € 0.10? Then it's definitely not big enough.
Again, an 7805 is wasteful and just not a good solution here. Forget about it, OK? Just use a DC-DC buck converter instead.
Thanks, much better. I'd place a 100uF (or so) cap at the output of the 5V regulator and also at the output of the 3.3V regulator.
I don't know what J1 and J2 are for so you're on your own in checking if they make sense like this.
I do see that you have tx/rx on the ESP01, the Arduino and on J1. I think you need to check that:
- Do the tx/rx of the various elements connect together appropriately? E.g. does the ESP01 TX need to connect to RX on the Arduino, perhaps?
- How are you going to deal with a Serial bus with 3 nodes instead of 2?
I'd place a decoupling capacitor on the Vcc of the WIZ850IO. Also check the datasheet if pin 9 needs to be connected or not; you're leaving it floating now. Since it's next to pin 8 anyway I'd just tie them together to be sure.