Frits breeding gear is a bull bit (so different from his riding/showing bit that he understands what it is for), a good quality webbing halter (his every day ones are PVC or rope halters), piece of polly pipe (just incase lol) and a nice long lead rope to give him space. This was advice given to me by a breeder in UK.
Another thing about AI is you have to teach the stallion to mount a dummy mare and also collect the swimmers, so you will need help with handling unless you are an octopus lol. Although there are vets and studs that offer this service.
Colts as yearlings can do the deed but mainly they are just testing the theory. However if he is penetrating mares then this could be unhealthy and spread STDs. Pregnant mares as a general rule are great to put colts in with as they generally don't allow for such shanannigans! However some mares are just tarts
There are some good books about breeding available I recommend that you get a few copies so that you can get as much info as you can
Hopefully some more experienced stallion owners will be on soon and give you much more info
