I understand budget, but at some point you need to factor in quality of life and time in Japan. Sure the Keisei Limited express for 1000 yen to the Yamanote on the way to Ikebukuro makes sense.
But for about 3000 yen vs 1210 (maybe) jumping on the NEX at Shinjuku for a straight, efficient, and easy shot to Narita may be worth the extra $15.

Scho