If you want a financial data subscription to be merely inspired by things you hadn't thought about, stick to spending $0, or 1% of your capital.

If you want a financial data subscription to actually get specific data that supports a specific edge you already perceived, spend whatever you think your edge is worth that gives you enough left over for a consistent profit.

Your perception is accurate. Come back when you have enough money to play.

Two great answers are provided, and I would like to add something. Most people do not wake up with 20K and say "tomorrow I will start investing".

They start small with regular systematic contributions. This might take the form of $50 auto drafted from your bank account corresponding to your pay days, or in 401K investments through payroll deductions.

Whatever, just start. You won't be optimal, and that is okay. Just get started picking some low cost index mutual funds from a reputable broker like Fidelity, Schwab, or Vanguard. All three have zero fees for most necessary transactions.

One of the best things a young person can do to secure their financial future is to find a way to earn money beyond your regular job. This can be anything from delivering pizza to ebay to scrap metal. Whatever, then use all of that money to build an investment account.

Doing such does not require one being born of privilege, a college degree, or much intelligence. Living in an area with economic opportunity helps greatly. It does require discipline and gumption. To top it all off there is a bunch of us old people that will gladly encourage and give good advice for free.

Consider how much value you're likely to get from any form of investment advice.

If you don't subscribe to anything, and do no research, but just purchase an S&P 500 index fund, you'll probably earn around 8% in the long run.

Now suppose you decide to pay for a service that provides investing advice (a publication or financial advisor). For this to make financial sense, you need to expect that following the advice will increase your earnings by more than the price. If the service costs 1% of the capital that you're investing, it needs to increase earnings by at least 1% (this is a bit of a simplification -- active investing can also reduce portfolio volatility, which is helpful in short terms).

But the situation isn't actually so bleak. Even if the increase in returns is not enough to offset the price of the advice, they compound over time. Eventually your portfolio may grow to a size where the cost of the service is well worth it. On the other hand, that will also happen with the index fund, so you might choose to wait until your investment grows to a size where it's worth getting more active.

However, there may also be non-financial considerations, as @BrenBarn mentions. Simply parking your money in a few mutual funds is boring. If you consider investing to be an interesting process, it will be more fun if you do it actively. In that case, you can consider subscribing to financial data similarly to a sports fan subscribing to Sports Illustrated. Even if it doesn't increase earnings to compensate for its price, you're enjoying the activity more.

Another factor is that as the size of your portfolio increases, more investment avenues open up for you (e.g. hedge funds). Many of these investments have eligibility requirements: minimum net worth and initial investment amounts. These types of investments are also more complicated, and you should seek out advice before considering them. The price of this advice is likely to correlate with the amount of your capital that you're investing.

For newsletters and advisory services, once upon a time you could get a free sample. Today, I think that many are geared toward a small free trial period or monthly subscription.

The most valuable one to me was one that I subscribed to in the late 1990's for $300 a year. It ranked first day IPO performance with a high degree of accuracy. I had access to many IPOs then and it was counter productive to have 'dead money' tied up in a crappy issue, as compared to an issue like Calloway Golf at $20 that opened up at $35.

Another aspect of this is time. Every some number of years there's an opportunity in preferred stocks due to interest rate gyrations (see the inverted yield curve fear of two years ago). Maintaining a database is worth the effort during such periods but doing so in the interim years is tedious. There's a chap who wrote a good book on this, contributes occasionally on Seeking Alpha and has a worthwhile fee based online advisory site with all of the data details of preferreds (Moodys and S&P ratings, call date, maturity date, dividend, cumul, non-cumul, etc.). For me, it's well worth an infrequent one month subscription for $30 to capture his data, saving me many, many hours of work.

The short answer is that you should subscribe to anything that either saves you a significant amount of time or increases your return with that increased return handily exceeding the cost of the subscription. The process of finding that source is the tricky part.

There is a fundamental rule that applies to every decision making process:

If you don't know what you are going to do with some piece of information when you have it, don't waste time and money trying to get it.

So unless you know how you are going to use this financial information, it isn't worth having even if it is free, because you will be wasting time looking at something you don't understand.

If you already have a strategy and you are confident using Value Line data will increase your profit by more than $600, then paying $600 for the data might be a good use of your money.

But if you just have the vague feeling that "knowing more stuff will help you make better decisions", don't bother!

The "trading information disease" - TID.

Humans en masse and on average behave in predictable common ways.

(Random example: there are now some four million people who have made an "app! on! the! app! stores!" because (i) about 8 (sic, that's eight, 12345678, ten minus two) people have become millionaires from apps and (ii) everyone knows that anyone can easily become a millionaire from an app.)

When

(A) a human gets "trading fever"

then

(B) almost always the human also gets TID. They become obsessed with finding that "secret piece of information that will allow them to become millionaires overnight by Trading!"

subsequently

(C) it is incredibly easy to make money based on (B) in the obvious way. Just sell any information in any format (newsletters, Professional! Level! Feeds!, blogs, books, PDFs, talks, 800-lines, whatever - makes no difference) to the people in B.

If you want to very easily make really great money from trading, just do what it says in C.