28 here, started my Roth IRA around 20 and maxed it out every year the first 6 or so years, been adding less aggressively since then because now I have some 401K matching at my current job and I put about 8K a year into that so the money I put in the IRA is much less than before. Time is on your side. BUY AND HOLD. Buy across industries. Don't put all your money into tech or gold or only US held companies or target date funds. Shit I don't like target date funds much at all tbh. I have a few funds and ETFs but the best thing I ever did was read a book on deep value investing, take the highlights, and invest in solid companies.
DO NOT mix emotions with investing. Like Mark said, don't bail when something goes a little south, simply buy more at the discount
Another tip, buy into necessary goods and services. I read that in a book years ago and it clicked. What do people need to survive? Look into those industries then pick decent companies that aren't overvalued, look to have a bright future, have the cash on hand to overcome obstacles, and have a decent track record. Think shelter, transportation, food, clothing, personal hygiene, pharmaceuticals, etc. Some examples that have been crushing it for me are General Mills, Home Depot, Honeywell, Hershey, Johnson and Johnson.
Although, tech companies are my biggest gains. I've held on to Apple, Google, Amazon, and Tesla for years and they have been ridiculous. I held Netflix for a long time too and made a ton on it and finally ditched it late 2019 due to the additional market pressure and their lack of a unique value prop recently.