Best Option for Private Pilot to Multi Commercial Instrument Ratings

I am currently a ASEL private pilot and would like to get to Multi Commercial
Instument ASAP. I can dedicate full time to this and would like your opinions
on the best way to go about it.

There seem to be 2 schools of thought -
1- get my instrument and commercial in a Single Engine, then get my multi add
ons.
2- Get my multi first, then work on instrument and commercial in the multi.

I can understand the pro's and cons to both. Option 1 allows me to work on one
thing at a time since I am already comfortable in a single engine, however it
might be detrimental b/c I won't have any appreciatable multi time when I am
done. This will lead to problems with insurance rates if I am insurable at
all.
Option 2 on the other hand will be a more expensive option, and will require
learning a few new things at the same time, but will also build 150 or so hrs
in the multi when I have my ratings which will certainly help insurance
companies.

Additional info - I am currently at about 185 hrs. I am not looking to go to
the airlines, but rather I am looking to fly a Cessna 421 for my company.

Any suggestions?
thanks,
Mark