Six years of membership, five add-on's, one rental and one transfer later, it's safe to say I will always want more trips than I have the points to cover...
Probably the easiest of all the "routes" I've taken were the add-on's...of course, that was also the most expensive of my choices--but I've found I use the add'l points so I don't feel bad about those choices...all my add-on's are small (biggest was 115 points--then one 100-point add-on, then 3 50-point add-on's)...worth noting I did all my add-on's before Disney started charging for closing costs--not sure I'd add on "in dribbles" any more given the closing costs now...
Short of adding on, either renting points or a points transfer if you find the "right"
DVC member to rent/transfer from can be a super choice...I found a terrific person -- he made a reservation for me for one trip, and did a points transfer for me another time...can't rave enough about him!
One difficulty w/the points transfer is that transferred points are sort of "step children" at MS...they don't show up in your online account, and it can be complicated to keep them straight if you don't use them all, all at once, when you first get them (I decided, since you can only have one transfer per use year, to get "extra's"--I did wind up using them (happily!), but they were considerably more trouble (for MS and for me!) to keep track of...)
The rental was super easy for me and my renter was absolutely wonderful about making the contacts I needed made at MS (to get MS and the dining plan), but I do prefer being in charge of the reservation myself...a control thing, probably, as I had no problems of any kind w/my renter...
If you're just a few points short you can do the one-time points purchase from Disney...
I've also reserved thru MS on the member cash plan (discount was available both times), but not because I was short of points--but because one of my nights wasn't available. Both times the W/L came through and the cash price was credited back on my credit card when the cash reservation was canceled after the W/L came through...also an easy process...
Good luck!