I'm going to pose a scheme, an outline, for investment considerations.
In an ideal world, someone who wants to invest would follow some steps (and some have little directly to do with actual dollars):
1) Complete and notarize legal paperwork if >18yo - Will, Living Will, Power of Atty for medical and legal needs.
2) Know cash flow and if it isn't + every year, budget behavior so it is (spend less than take home, invest the rest).
3) Work retirement benefits - contribute up to the full match on any employer tax-differed benefit (401/403/427/TSP/etc). It's a free raise -- with rare exceptions never decline it.
4) Build an emergency/oh-sh*t fund through a CD ladder, I-bonds, and savings/money market account for at least 3-12 months' worth of budget in #2.
5) Health insurance - for the vast majority of people, choosing a HDHP plan that allows HSA accounts is sufficient. If it's right for your needs, open and contribute to a HSA investment acct up to the max allowed by IRS. HSA savings accts aren't the worst choice -- but they pay interest<inflation. (The worst choice is no insurance, the second worst choice is too much insurance sold by fear.) If interest rates on debt are > than average gains from HSA investments, allocate more to debt than HSA and/or #7 or #8.
6) No debt -- if one is in debt, change habits now to start paying it down every month, no exceptions. If interest rates on debt are > than average gains from investments, pay debt before further investing (except for #4 & #5 - do simultaneously).
7) Explore ROTH investment accounts, and contribute up to the IRS max allowed.
8) Self-employed need to discover SEP-IRAs and alike.
9) Live.
Personally, I'm a huge believer in long-term very diversified holdings such as VTI. Everyone needs to discover their own comfort zones and there are thousands if not millions of web posts, books, podcasts, pundits, courses out there. One doesn't have to spend a dime on ANY of them - most are free to download, listen, check out at the library. Keep learning -- but don't let analysis paralysis stop you from doing something today or this week. The people who don't ever start are the ones who always wish they had. The power of compounding is in your youth or my yesterdays.
With the above tackled, and you're doing that Living thing, one may consider investing in taxable accounts, or upping their work retirement program, or investing in other ways (education, play, charity, your own business/real estate). I don't consider a home mortgage to be a debt to pay off ASAP unless it's interest % > investment gains. Heck, I'm not sure owning a home is always a great idea, as renting has real $ and non-tangible advantages in the short term.