I entirely self-manage, for the past ~24 years now. That involves a persistent investment of time for a lifetime (a never ending process of reading and learning), and I happen to enjoy it. I could never stand to pay someone else to earn mediocre returns on my money. It's a beautiful time to be an investor, between zero-fee trades and easy access to a lot of excellent information and tools (in most cases now packaged with a common brokerage account).
My advice would be to do exactly what you're doing in regards to index funds, since this is your first money going into the market. If this very richly valued market drops at some point, it's going to sting, don't let that dissuade you from the long-term course, which is: investing as a matter of routine over time, you're in it for a lifetime, not a short-term flip; and during that lifetime, there will be many ups and downs. Always do your best to hold a long-term mentality about what you're trying to accomplish.
Depending on your personality, your preferences for learning about investing and managing your own money (it's incredibly boring to many people in my experience), you might consider setting aside a small slice of your investment money to invest into specific companies that you're interested in (ideally sticking to higher-quality, well-known, longer track record companies, so as to improve your odds of avoiding the Nikolas out there). Use that stake as a self-interest booster to practice reading about a company, following their progress, read their financials, read their quarterly and annual reports, read some of their archived annual reports. Practice basic due diligence on an investment that you're interested in (eg AMD, whatever it happens to be). Get used to the terminology, teach yourself to be able to digest financial information about companies rapidly, so that it's second nature. Then with a better grasp, begin practicing comparing companies, which will help you build some baseline comparison capabilities (so you'll be able to more rapidly grasp good or bad numbers from a company). Occasionally read business news, although don't bother with the bulls & bears type junk, the clickbait of the business & financial news world; read about concepts and events (like mergers & acquisitions, or stock issuances, IPOs, conflicts), to further educate yourself about how the markets work and get a feel for that world. This basic learning aspect doesn't take a lot of time, an hour per week, kept up over time. The end result is extremely valuable: considerably improved financial literacy; it gives you a leg up, as the vast majority of populations even in affluent nations tend to have a weak understanding of financial markets and stocks.
I'm biased in my recommendations, I'm a modified value investor in terms of strategy. I look for what I perceive to be mistakes in price vs value in the market. If you have an interest in managing your own money over time, you'll likely gradually learn to lean into what you're good at.
I'd recommend a few introduction level books, from the perspective of my bias:
Buffett: The Making of an American Capitalist, by Roger Lowenstein. Not primarily to learn about Buffett, rather, to learn about the concept of value as it pertains to investing.
Business Adventures: Twelve Classic Tales from the World of Wall Street, by John Brooks.
The Little Book That Still Beats the Market, by Joel Greenblatt.
Margin of Safety, by Seth Klarman. This book is excellent, however it has been out of print for some time. You may be able to find a copy of it somewhere though (there have often been PDFs of it floating around).
Common Stocks and Uncommon Profits, by Philip Fisher.
Peter Lynch has a few worthwhile books as well. Some of this will seem out of date, it's not. The lessons are eternal.
A lot of people will jump to recommending The Intelligent Investor by Benjamin Graham, I absolutely do not recommend his books for anyone new to investing. They're extremely dense, even for an average investor with years of experience.
I'd read this article by Warren Buffett from 1984 (The Superinvestors of Graham-and-Doddsville):
https://www8.gsb.columbia.edu/articles/columbia-business/sup...
There is always a wave of people that come around during the heady days in markets, proclaiming that value investing doesn't work, that markets are too efficient or the like. In the 1984 article (linked above) by Buffett, he references this as well, it was being argued to be an out-of-date approach just the same four decades ago; one might be inclined to question the authors of those arguments for what they're revealing about their particular interests. That's all bunk. I made a killing buying in March during the brief crash, by doing nothing more than specifically taking advantage of the sudden and considerable price vs value discounts that were made available (like Square trading for a mere three to four times sales; a belligerent discount vs their growth and potential), an inefficiency event in the market. It's down to being able to stand apart from the emotional crowd and make your own determinations about value. The approach will always work, and it applies to everything we do economically throughout life, not just investing in stocks.