What genre do you play or listen,for me i play rock , metal songs on rocksmith usually their riffs are pretty easy and sounding good without band. I can only recommend some metal or rock songs, you can play Cowboys from hell from Pantera its kind of easy and good sounding when played alone, you can try to learn some easy melodic solos like Master of Puppets interlude solo played by James Hetfield. I can help more if you tell me which type of music you usually listen to.