Hi, i was wondering what peoples tips are for breeding.

I want to have hurdle/fence horses that will hopefully be able to win feature races at cheltenham festival

what sort of horses should i be breeding? what age? what quality?

any help would be most grateful

Basically good quality breeds good quality.
You just have to breed your best horses within each distance with each other. Go for the horses with most G1 wins and highest ratings. You also need to take your time doing this by building your barn gradually over several seasons.
Have patience and you will succeed!
Sometimes you will see that some of your top horses are not breeding well, and some of the mediocre horses are breeding winners. So it's not just plain mathematics, it varies just as in real life.

A load of good advice you will also find in this forum just by searching for topics. Take some time researching what advice have been given already.