New lawn

Just bought a newly constructed home in north Idaho. The yard is clay, the contractors put some gravel down to fill some low spots. I'm trying to figure out what would be best to fill and level some spots and what to use to get lawn started in the spring, tires of the muddy mess. Seeing if I need gravel, top soil or what, both. New to home ownership and landscaping. As miucj info would be best. Thanks in advance