In practice, I would spread my bankroll over as many bookmakers as possible with a few constraints.

1. I always want to max out a deposit bonus. Deposit bonuses vary from anywhere between $100-$300. Before depositing at a bookie with a $300 bonus, I’d wait until I’m able to max out that bonus.
2. I want to spread my bankroll disproportionately, where I have a larger % at bookies with a larger number of trades and a lower % at bookies with a lower volume of trades. E.g, I might place 2/5 of my bankroll on higher volume bookies, ⅕ on lower volume bookies and keep ⅖ in reserve in my bank account or e-wallet until I get a more clear picture of which bookies I get the highest volume of trades in and also in case I run bad at a bookie and tap out there. The goal being to eventually get my entire bankroll in play in order to maximise my turnover.
3. The bookmaker needs to accept customers from your country. This is something you will have to check yourself.