What do you value the most - training or hands-off? A brokerage like Keller Williams that has a ton of in-office training and management available will often cost you more in your split and your monthly payments, but also give you more opportunities to find agents you can help with Open Houses, etc. If you want to do your own thing (very difficult for new agents who want to get business) you can look at high split agencies, but they don't have the same level of training and management usually, but there are exceptions to both rules.
I've worked for Keller Williams (70-30 split when I started, but newer agents can start 60-40), Berkshire Hathaway (70-30 negotiated, new agents start 50-50), Sotheby's (I was on a 90-10 because I had a team of 15 under me), and eXp, which I like the most, because they give me the most freedom (80-20 split and a low cap).
If you are new and want to learn and network and get opportunities for mentorship, the bigger box brokerages are better starting points in my opinion, but you will pay for it. Hope that helps.