If you want to learn to be good at philosophy you need to come at it with two things. Firstly you need self-direction. You need to be curious. To have problems you're interested in. To be willing to think for yourself. Secondly you need to have a very good understanding of philosophy's traditions. You're only ever one of the latest people to learn something, and as that person, you're one of the least well informed.
Both are crucial, but it's easy to prefer one over the other.
It's common to find self-direction scary, and it's common, if you do have self-direction, to sometimes be so sure of your own thoughts that you underestimate the value of very thoroughly learning why traditions can show you up.But if you can learn to have both, the one keeps the other in its toes in just the right way.
For these reasons a philosophy degree CAN be the best thing to do. I say 'can' because it's so easy to screw up at it. You can screw it up by not doing a good combination of these two criteria.
Firstly, it's not school. you're not told what to think. You're teacher is no longer a straight up authority, but just some guy who happens to really be familiar with the papers you're looking at for this philosophy problem. You can challenge him, you can challenge the papers, and you can challenge your fellow classmates. Better still, you're encouraged to do this.
And you get a lot of choice about what you're going to learn. From what university to pick (for instance, I like the University of Manchester because it's very cutting edge), to what units on the degree program, and THEN even what parts of the unit you're interested in (because you can choose which part to do your essay on and which part to bring up in your tutorials).
But it isn't exactly bespoke, as learning as an autodidact would be. It's more like going to the supermarket or ordering from a menu. But that's good, because that's where the second criterion comes in.
Once you know what problems you're most interested in, you'll get given a reading list on that subject, and it's this that turns out to be worth thousands of pounds, believe it or not. Very few people understand the arguments in philosophy well enough to recommend you a good reading list. Very few people have even heard of the philosophers you'll be looking at. The amount of knowledge and understanding of philosophy that goes into those reading lists is huge. But a reading list is nothing by itself, after all, they are actually online. It's the fact that the entire university experience is dedicated to that reading list. Philosophy is hard, *and* full of contexts and subtleties that are easy to miss. You don't just need the reading list, you need someone to help you understand the reading list and it's readings (which is what your lectures are for). And then, you need someone to work with to challenge the reading and the reading list (which is what your tutorials are for, in part).
Used right, philosophy degrees are a genius combination of what you need to be good at philosophy.