I have reasonable undergraduate and graduate background(just ode & pde part is horrible).I want an introductory book that doesn't just list some ways to solve a bunch of equation.I want it to give me ideas necessary to make the ways feel reasonable and also keep things rigorous.I have no problem using different books for rigor and ideas.Also,a book of geometric flavor or connecting geometry to it would be very good.As, geometry is the main reason I am studying it.Thank You.
edit:it's not duplicate.I think I asked for something more than the answer's there provided.