Osoto-gari is one of the most basic of judo throws. It's one of the first few throws taught to beginners. Unfortunately, the classical or traditional way osoto is taught is very flawed.

Usually, tori is taught to take a step first with their supporting leg, only to be followed by the attacking leg. This will not only cause uke to withdraw their target leg, it also puts uke in an unbalanced situation.

It is always better for tori to take the first step with their attacking leg. In an right vs right kenka-yotsu situation, tori should take a first step with their right leg, followed by a slight backstep with their left leg, and then attack with their right leg.
So, it's Right-Left-Right.

It helps if tori's body language suggests that they are about to do a forward attack. This causes uke to pull back a bit, which is the direction you want them moving in as that is the direction you want to throw them.