My friend, you need to read the Motor controllerl tutorial here:
http://www.societyofrobots.com/member_tutorials/node/159 and the PWM tutorial here:
http://www.societyofrobots.com/member_tutorials/node/228I don't know the pin settings for the $50 robot so I can't tell you what pins you should use, unless you make a list and post it here, I will not look it up for you. But here are the pin settings I use in my dual motor controller using tiny2313:
// Module Arduino Pin Tiny2313 Pin Arduino Module
// +-\/-+
// Reset PA2 1| |29 VCC
// RX (D 0) PD0 2| |19 PB7 (D 16) SCL (SKC )
// TX (D 1) PD1 3| |18 PB6 (D 15) (MISO)
// Xtal (D 2) PA1 4| |17 PB5 (D 14) SDA (MOSI)
// Xtal (D 3) PA0 5| |16 PB4 (D 13)* M1A (OC1B)
// Enc1A # (D 4) PD2 6| |15 PB3 (D 12)* M2A (OC1A)
// Enc2A # (D 5) PD3 7| |14 PB2 (D 11)* M1B
// Enc1B (D 6) PD4 8| |13 PB1 (D 10) M2B
// Enc2B *(D 7) PD5 9| |12 PB0 (D 9) M2En
// GND 10| |11 PD6 (D 8 ) M1En
// +----+
//
// * indicates PWM port
// # indicates external interrupt
//
// M1 = RightMotor
// M2 = LeftMotor
// E1 = RightEncoder
// E2 = LeftEncoder
Module is my board, so that is the function of the pin in my board. Arduino is the name of the pin in Arduino and Pin is the pin name by data sheet.