Microcontrollers

ESP32


1 piece: ~$4.70 from aliexpress

Arduino Nano


1 piece: ~$5.50 from aliexpress

Sensors & Peripherals

OLED Display


1 piece: ~$1.65 from aliexpress

Photoresistor


50 pieces: ~$1.25 from aliexpress

Capacitive Soil Moisture Sensor


1 piece: ~$0.40 from aliexpress

Time-of-Flight (ToF) Laser Ranging Sensor


1 piece: ~$1.50 from aliexpress

Ultrasonic Sensor


1 piece: ~$0.90 from aliexpress

RTC (Real Time Clock)


1 piece: ~$2.30 from aliexpress

Digital Temperature Sensor


10 pieces: ~$2.70 from aliexpress

Temperature / Humidity Sensor


1 piece: ~$2.50 from aliexpress

Electronics

Breadboard


small: ~$1 from aliexpress
large: ~$1 from aliexpress

Jumper wires


40 pieces: ~$1.60 from aliexpress

Wires with Alligator-Banana tips


1m cable: ~$0.70 from aliexpress

Resistors


600 pieces: ~$2.40 from aliexpress

Potentiometer (variable resistor)


10 pieces: ~$1.70 from aliexpress

JST (pin header connector)


230 pieces: ~$0.70 from aliexpress

Relay


3.3V 2 Channel Relay Module: ~$1.30 from aliexpress

Helping hands


~$16 from aliexpress

Operational amplifier


10 pieces: ~$2.20 from aliexpress

Toggle switch


40 pieces: ~$1.80 from aliexpress

Prototype PCB (Printed Circuit Board)


10 pieces: ~$1.20 from aliexpress

Heat Gun


1 piece: ~$9.00 from aliexpress

Heat Shrink Set


328 pieces: ~$3.00 from aliexpress