I say pick one breed, and concentrate on quality, not quantity. Our family has been raising Maine-Anjou show calves since 1990. Our girls finished showing in 2000, so we are out of the show ring now.
I was given the best advice I ever received about Showing in 1991 when a business associate said to me "If you want to do this right, and get really good at it, you have to get your kids to the National Junior Show, get involved in the Association, and get involved with the State Association too. You'll never understand what great is until you compete with, and against the great ones".(exact quote).
We loaded up that Summer,(with almost no knowledge of what we were doing) and went to the NJMAA in Kearney, NE. We did the same thing each Summer for the next 9 years. Our girls are now grown, married, and have kids of there own(Living in NW Arkansas). To this day they will tell you that their best memories growing up were all from the National Shows.
We still did the local, county, state, and jackpot shows; and won at all of them with cattle we raised. We never would have known what Great is, if we had not learned it from the Great ones.
The girls also received some tremendous scholarships from the AMAA and OMAA. It would have been next to impossible to reach the level of performance we achieved had we been showing more than one breed.