I bake 10" cakes in two layers. It's much easier and gives a nice deep cake.
For a 10 " I do 5 eggs per layer which produces a cake that's about 1.25 − 1.5" deep.
4 eggs give you a layer about an inch deep.
I make celebration cakes so usually trim the top of each cake before I sandwich and ice them so I have a perfectly flat and level cake, hence the deeper layer to begin with. If you're happy just to slap the layers together then a 4 egg mix will be fine.
I know lots of people swear by the 'chuck it all in a bowl and beat' method but it doesn't work as well as the creaming method, for me.
For a 4 egg mix, I use 8oz Stork and 8oz caster sugar, plus a splash of vanilla essence. Beat with a hand mixer or KitchenAid thingy for 5 minutes until it's pale and fluffy.
You'll need to use 4 medium eggs and 8oz self raising flour - add the eggs one at a time with a heaped tablespoon of flour and mix well before you add the next one. Mix in the rest of the flour, pour into tin and cook for 50 - 55 mins in a non-fan oven preheated to 160 degrees.
Repeat for the second layer.
Spread the top of one layer with jam and the bottom of the other layer with buttercream and sandwich together.
Spread buttercream over the top as well, if you want to be able to stick stuff to it.
If you do a 5 egg mix you'll need 10 oz each of butter, sugar, flour.
Good luck!