ESP8266-07 variant has an external antenna. I have used an ESP with a standalone Mega 328 for a weather station (quite similar to what you want). The 328 is used , as a peripheral of the ESP, to interface with the sensors and I use a software serial connection to the ESP to send the data to the ESP and the ESP runs a server. I recommend that you get an Uno and some of the sensors that you will use. Break the project into small parts, write sketches for each piece and add the pieces together as you develop experience.