voltaire has an amazing conditioner! it's a little pricey but it's amazing for breaking in tack. it's also really good for conditioning tack that hasn't been taken care of in a little while.
Belvoir Tack Cleaner, Conditioner, and then balm. The brand is Carr, Martin and Day I believe.
I use a everyday leather cleaner that I get from the supermarket first and then use either effax leather balm or an oil by equipe
Fiebing's is about 5 dollars and it works well for me
I like effax a lot because it is affordable and works really well.