This basic combination is a requirement when testing from 4th kyu purple and white belt to 3rd kyu brown belt.
We have two combinations, the other being, mae geri, mawashi geri, gyaku zuki, gedan barai. both of these combinations work on the same fundamentals, which are, keeping the hikite and blocking arm in position whilst two kicks are executed, shomen (square facing) hanmi (side facing) and making the combination continuous.

1. Start from a hidari gedan barai ( left side downward block)
2. Whilst keeping the arms in the same position, kick mae geri (front kick) with the right leg.
3. Drive off the left leg and take a step forward (you can vary the distance of the step), then whilst keeping the arms in the gedan barai position, kick mawashi geri (round kick) with the left leg.
4. Recover the kicking leg then drive off the right leg and land gyaku zuki (reverse punch) with the right arm.
5. Then turn and repeat on the opposite side.

Mae Geri, Mawashi Geri, Gyaku Zuki, Gedan Barai Video Tutorial