Let’s make it easy for your first dressing.
3 Tbs. oil;
1Tbs. vinegar;
Salt and black pepper;
Pour first oil in a large bowl, then add vinegar. Whisk well. Season to taste with salt and pepper. On the top, add 6oz of mixed greens or mesclun salad and toss well before serving.
My Green Salad 
Add the greens (6oz) on the top of the dressing and mix everything together 10 minutes before eating. Then mix again just before eating.