First let me preface all this by saying it would be irresponsible to tell writers not to have a portfolio of scripts. Writers should be cranking out 2-3 scripts a year. It’s wise to have as many tricks up your sleeve as possible (though I will continue to preach that new writers should pick a genre and stick to it). Increasing your output of scripts increases your odds of stumbling upon your one script that will open the doors to a professional career. However, IMO, "portfolios" are more important for the writer than they are as a sales tool.
Most agents only sell one script at a time.
My guess is that there aren’t a lot of writers who’ve sold three or four scripts in a single swoop, so having a huge portfolio doesn’t mean anything in the marketplace. (As an aside, TV agents will look for a portfolio of scripts from aspiring writers.)
Feature agents are far more interested in one saleable script than a portfolio of twenty unsaleable scripts.
If an agent finds you have a script he can sell, one script is enough. When he sells the script, he’ll set you up with studio assignments. If you have old scripts that are potentially saleable, he might ask you to clean out your closet to see what you’ve got. But assignments are a more reliable way to earn a living (and a commission) anyway. Ryan Condal, who recently sold GALAHAD (first-time spec sale), has already landed two coveted assignments. His income is set for a while.
When studios or producers get a script they want to buy, they aren’t going to waste time reading previous efforts by the writer or combing his “portfolio.” The one script will do the job.
Any respectable agent or manager would avoid the “Whatcha Got Next?” sales technique to sell a spec script. (“So you don’t like that script…how about this one? You don’t like that, huh? How about this one?”) Most sales are a planned, strategic attack that target specific buyers who are most likely in the market for a certain piece of material. We're talking about hundreds of thousands of dollars at risk. This isn't a garage sale.
If an agent likes a new writer but knows he cannot sell the script, he might ask to see other scripts. However, it’s unlikely that a new writer will land an agent without a saleable script unless he comes highly recommended from respected co-workers or the writer has some heat - like he’s won the Nicholl Fellowship (with a script that will never sell). An agent would be more likely to take a chance in that kind of situation, but if a writer comes to the table without a saleable script, without heat, and no juice - representation (from a real agent who can move a career) is unlikely.
Having several scripts - a "portfolio" - (in one genre) comes in handy when a producer is looking to hire a writer for an assignment.
After setting up a pitch at Paramount, we needed to find a writer. We familiarized ourselves with writers (well-suited for our material) and read, at least, two scripts by each writer. (April Blair was eventually hired to write the script.) This is an example where having several scripts was crucial.
However, these writers were not just any writers; these were not INKTIP writers. These names came from a "studio list" of approved writers. (Writers that the studio believes have shown excellence in a particular genre - which is why it is so important for a new writer to brand himself).
But in order to get your name on that list, you will need to sell a script, make an unforgetable impression on an executive or light the town on fire. (Remember, nothing impresses the town more than selling a spec.)
I hear what you're saying, zero, but the truth is that you were never going to sell a script to a producer in the room anyway. You could have pulled 80 scripts out of your ass and nothing would have happened.
As an aspiring writer without representation, the odds of selling a script or getting an assignment - for a real producer with real money - are slim to none. (There are always exceptions, but this would be a very tough game to win.)
Trying to sell scripts to producers directly is a much tougher job than even getting representation. In the old days, studios ran the business, put the deals together and made the movies. Nowadays, it’s the agencies. Without representation, you will most likely spin your wheels for a very long time. Some writers survive without reps but these might be scribes who are already well established or writers who deal in a small network of genre specific DVD Original producers. (And they don’t pay studio money.)
IMO, I don’t think your mistake was not having back-up scripts as much as it was presenting the producer with a script he didn’t want to buy (which means a script he couldn’t sell as a movie).
New writers should be writing their asses off, but it must be a smart effort. Without an attractive concept in a script that can potentially sell (and 99.9% of aspiring writers haven’t found the combination of concept & craft), having a portfolio with all the scripts in the world is meaningless.