jab - right hand - roundhouse (bread and butter technique practise this with double roundhouse also)
jab - left hook - right hand - roundhouse
teep (step forward as you land) - knee to body
as someone said before - start with hands finish with kicks/knees
work on distance and closing it. also what combos work best depend on your body type ie do you have long/short arms/legs etc.
theres so much variation for example the teep tends to be a defensive kick but if you teep someone against the ropes you could catch them as they rebound with a nice roundhouse/flying knee/superman punch (mmmmm pause to contemplate!!)
keep training and trust your coach!!