My first investing experience was a terrible one!
I was a naive 16-year-old, and my parents gave me $2k and said "go make us rich". (Pro tip: parents, do not do this, it will not work.) I plowed it all into the Telstra 2 share offering, wherein the Australian government stuffed nearly every single retail investor in the country with shares in Australia's former monopoly telco at the ding-dong high of the dotcom bubble.
I chose... poorly.
They got the IPO away on a 7 handle and it never traded there again. It took
thirteen years for anyone who bought Telstra 2 at the IPO to get back to flat,
including dividends. Let this be a lesson: stagging IPOs is occasionally a terrible idea.
So that sort of scared me off investing for a long time, and scared me off single stocks forever: my working assumption now is that I suck at stockpicking so I should resist the temptation to trade single stocks. I basically kept all my cash in the bank from 2000 to 2008, which in hindsight was dumb - I'd have done better to buy and hold through the GFC.
That said, it was pure dumb luck that I wasn't
BOLIVIAN long when everything fell out of bed in 2007/08; when everything dumped 30% I thought "gee maybe I'd better get around to opening a brokerage account like I've been meaning to". I bought a bunch of index ETFs in October 2008, and then everything went another 20% in my face over the next six months.
But I'd been doing plenty of reading, and had to persuade myself that dollar-cost averaging - buying a steady amount each month - was the right thing to do. My absolute ding-dong low purchase was a clip of SPY at $71.02 in March 2009... and now it's about to crack $200. I still have those SPYs.
(The confo from that SPY trade is one of my favourite trophies. I still have a copy of it, along with my Reuters ticket for a clip of AUDUSD I sold at 1.0000 when it traded there for the first time in three decades. Took a LONG time for that one to go my way.)
That was how I got started with boring, sensible, low-cost, buy-and-hold index investing. I diversified over the next few years, jumping into an asset class whenever it got cheap - European stocks in 2011-2012 after the peripherals blowup; muni bonds in 2013 after Meredith Whitney shot her mouth off; emerging markets earlier this year after the Russia/Ukraine shenanigans kicked off. (I'm still looking for an opportunity to get long Aussie stocks - I'm technically underweight those, because I might end up retiring over there. I think it'll come when AUDUSD trades back to 70 cents.)