There are some fun easy riffs to start off with. From the top of my head:
Really easy: Don't Try Suicide, Action This Day, Son And Daughter, One Vision, AOBTD, Flash's Theme, My Baby Does Me, Get Down Make Love
Easy: AKOM, Dragon Attack, Under Pressure, Pain Is So Close To Pressure, I Was Born To Love You, You Don't Fool Me, the funky songs from Hot Space, Breakthru.
The Millionaire Waltz - John's easiest bass performance...just kidding.
Here are the songs I'd recommend:
Under Pressure, A Kind Of Magic, AOBTD, Fun It, Bring Back That Leroy Brown, Crazy Little Thing Called Love (The latter two are best played if you wanna have a little challenge with the bass)