The controller didnt give you enough info but since standard pattern entry is a 45 degree entry to the downwind the safe thing would be to do that, then report base. If he wanted you to enter direct to the base he should have said "ENTER left base".
I agree. Since the controller told you to report left/right base, how you get there is up to you. Granted, if it was a right base some sort of entry instructions should have been given as well, as only left turns/entry can be omitted. "Make right traffic, report base" or something along those lines. Still, since it's not specified where to enter the traffic pattern you get to pick. Either report entering the base directly, or report turning the base from the downwind.
As to reporting points, it's been a bone of contention for as long as I've been a controller. A lot of it is technique in regards to what the controller is actually looking for/doing by issuing the instruction to begn with. If I am asking a pilot to report something, it's not to reference that aircraft, nor a reminder to issue that pilot a clearance. It's part of my mental checklist to ensure the other factors in play are what they need to be.
If for some reason I issue a pilot a reporting point, and they do not have a clearance, and then I go bact to issue a clearance prior to that reporting point, I
personally do not care if they don't give the report and normally will state as such "NXXX, RWY XX, cleared to land, no need for the base report." If they report anyway, that's fine too. Wrong, right, or indifferent: check the AIM for the 100% answer. If however, I still need the report, while issuing the clearance I'll restate the request using emphasis for clarity. "NXXX, number 4, follow traffic ahead in the downwind, runway XX cleared to land, report turning base." Something to that effect. That leaves no question about "should I or should I not report" and it's served me well.
But again, that's just me - personally. I've found over the years that adding in a quip of phraseology to leave no question to what it is that I'm expecting is more efficient that cleaning up the mess when it doesn't go as anticipated...and that goes for a lot of things other than reporting points and pattern entry procedures.