I think I've done 1. Not very common, and you'd have to have a specific set of circumstances for it to make sense.
If you do you Multi first, then when you do your IR, you'll have to do at least one single-engine approach in a multi in order to not have a limitation on your certificate. So this means you either do your IR in a multi (expensive) or on checkride day, you hop over to the multi after you're done in the single (adding complexity to the checkride, and you had to train to do it anyway - expensive).
In addition, insurance for a multi non-IFR pilot will be tougher and/or more expensive to get.
One situation where it can make sense is if you are a PP-ASEL, and want to buy a multi. Or have access to a family plane, or something like that, and initial cost of insurance is not an issue. You get your PP-AMEL in it, then flow right into the IR.