There are a number of brands/ranges that you can use. It must be remembered that the cheapest ammo WON’T shoot as well as the most expensive. That’s why it’s cheaper.The most favored ammunition for many, many years has been Eley, Lapua and RWS. These are consistently the best and they seem to take it in turns as to who this year will win the most events.
They all make a premium brand $23-$35 a box/50 (prices change with A$ movement), Mid range $15-$20. Low or Practice range $12-$8 and also a hunting plinking range $3-$6 can be used by very new shooters until they start to feel confident in what they are doing.
After saying all of that. I have seen cheap ammunition shoot extremely well and consistently better than the best that is to offer. If you find that there is a Type/Batch of ammunition that suits your rifle then purchase all that you can of that batch and use it for competition shooting.