The first gig of any tour is always loose and filled with experimentation. That why it should be a real kick to see 10cc start its “Ultimate Greatest Hits” tour on Bloomfield Avenue in Montclair July 24. Thirty million albums sold into a career well into its 52nd year, this British quintet is more than just “I’m Not In Love” and “Dreadlock Holiday.” Their sophisticated sumptuous melodic and harmonic trips are still totally swoon-worthy and THC-friendly.