All I can tell you is, if you have to ask, you're not ready.
Listen to this man.
I think you already knew this (the way you phrased the question implied that you know you're not ready yet), you're pretty clearly ahead of me, and I've been chasing exactly as long as you have. If you go out unsure but "faking it until you make it," like I stupidly did earlier this year, you end up getting yourself in situations that you don't know how to escape, that you assume danger where none is present, or worse, that you don't even recognize as actual danger.
Idiotic case 1: Last August, before I even knew a thing about chasing or weather, I drove to the southern part of my county to chase a tornadic cell that hit me straight-on after taking a right turn. Fortunately it had become outflow-dominant by the time I reached it (recalling in retrospect the massive front-line winds) but I was scared out of my wits and had no way to escape. Lesson: know weather basics and plan routes ahead of time.
Idiotic case 2: I chased a MDT by myself in Nebraska when my chasing partner had to work. Not only did I entirely ignore a tornado machine in Iowa because I didn't pay attention to storm motions (not Parkersburg, but a nice isolated sup in the southern part of the state) but I ended up quite close to, and nearly under, a bear's cage circulation because I thought what I was looking at was "just some turbulence." I'd figured nothing dangerous could develop on a flanking line. Foolish.
Idiotic case 3: I got a big head, ignored the pleas of my stormchasing partner, and drove south (i.e. the wrong way) during the Wakeeney tornado. We practically got blown off the roads by RFDs. I was lucky to not take a direct hit with my stupidity. Lesson: Always have an experienced partner with you until you're ready to do it on your own, and then LISTEN TO HIM/HER.
How long does it take? I don't know. I'm not there yet myself. Since the people posting on this site are almost universally on the same relative intelligence scale (however, intuition may vary), it probably depends on how much time you can spend a) studying and b) chasing. Geographic location also matters; certainly the dryline storms in Western Kansas, OK, W NE, etc., are far different than the quick-moving cold front late-Winter murderers in the Southeast and the wet, very dangerous late-Spring warm front HP's in Iowa and Illinois.
This isn't to say you can't chase on your own at all. How would you ever know what you're seeing while someone
isn't holding your hand? But you still have to be careful, and recall the lessons you have seen when chasing with a partner who is leading. Personally, I go out on stormy days when storms are high based, or elevated, or unsupported in the upper level and thus cellular/outflow-dom and highly improbable to become tornadic. This implies a bit of forecasting on your own, but learning that much hasn't been difficult or long for me IMO.
Without a book, it's difficult to study from the often-recommended Haby site. If you know little, like me, you'll find yourself shortly in a sort of infinite regress of link-clicking on that maze. It sort of assumes you at least know more than I do.
Then where to start? Personally, I purchased Tim Vasquez's Storm Chasing Handbook, Purple and Red Forecasting guides, the Green reference manual for weather maps, models, and satellites, and a program that has about 500 historical forecast setups as a sort of "stormchasing video game" for you to learn forecasting relative to chasing storms. I will go through those products in the order I gave them, and I plan to dedicate the next three months to them with the time I would normally spend for an average, undergradute semester-long course. All of this can be purchased from Tim V's site (don't try Amazon, they're sold out) for about the price of one single college textbook.
Since I got these in just today, I can't vouch for them myself, but a lot of experienced chasers have touted them. That's good enough for me.
Since I am myself a newb, I invite any kind of criticism from any of the vets here - and any advice from the OP's side of his first chasing year as well.