Buy components
Raspberry Pi 3 B+:
1.4 GHz 64-bit quad-core processor, dual-band wireless LAN, Bluetooth 4.2/BLE, faster Ethernet.
Price: 46$
VIVI PLEN2:
An interesting Humanoid robot suitable for college students, research projects, and geeks. It is the cheapest Humanoid robot as I know.
Geekcreit® NodeMcu Lua ESP8266 ESP-12E WIFI Development Board. I advice you to have several boards so you can test client-server communication and sensors network)
Price US$4.45
Geekcreit™ Doit 2WD L293D WIFI RC Smart Car With NodeMCU.
A kit where you have all the components to assemble your robot.
Price US$22.19
This kit contain 37 kit sensor. Most of them are easy to use with both Arduino or NODEMCU.
Price US$10.89
An interesting kit to assemble an advanced robot.
Price US$93.99
Price: 2.96$
Wemos
Price US$5.75
Price US$37.49
NodeMcu Lua ESP8266 ESP-12E + WiFi Motor Price US$10.83
This is 7 in one kit, it have 1 Wemos D1 Mini NodeMcu Lua WIFI ESP8266 Development Board,and 6 other module (Relay module, DS18B20, Micro SD Storage Expansion module,DHT module …) Price US$12.99
Price US$2.37
Price US$22.29
Price US$5.49
Price US$6.74