Should I make a Stocks and Shares ISA now?

I got 5k in my bank and an undergraduate and currently don't have a part-time job or anything. But I'm rly interested in investing and money and whatnot. There's a lot of hype around the ISA benefits before April 5. If I theoretically put in 1-2k in a stocks and shares ISA and leave it for a few years, it won't collect tax, right?

Do I also have to keep adding money every yr? Or can I leave it be until I have income and can add some more?

Its important to note that any form of investing carries it's own risks. Note that you are not guaranteed returns on your capital when you invest in a stocks and shares ISA.
Therefore, It's completely possible you might lose all (or a lot of) your money. Case in point:
Look at Nasdaq yearly returns, specifically during the internet bubble from 2000 - 2002. If you had invested £5k at the beginning of 2000 into a Nasdaq tracker, at the end of 2002 you would have been left with circa £1300. (source: Nasdaq 100 Annual Returns by Year (slickcharts.com) )
It's crucial you do your research, with careful consideration of your long term & short term goals. Just an FYI.
That said, you woudn't have to pay any tax on your gains from an ISA. You can deposit up to £20k every financial year into an ISA (cumulatively). So if you had £4k in a Lifetime ISA, then your Stocks and Shares ISA allowance would be reduced to £16k for that year.
You can leave it for as long as you want. Generally for stocks and shares ISAs, if you have a well diversified porfolio and market conditions remain mostly favourable, it's advisable to leave money for longer rather than shorter periods of time. Using my example above of an initial investment of £5k, even though you are left with £1300 at the end of 2002, if you hold till 2017 (with no other invested capital) your return should be around £8,300.
Hope this gives a bit of clarity between the risks and rewards of investing.

Yep, it certainly has, thanks! I've made my ISA and just dropped under 1k into the vanguard S&P 500 for diversification because I don't want to move too fast and instead take time to learn about the stock market before deciding on anything else.

It may or may not be prudent, but the S&P 500 index has proven to beat practically every other index and ETF out there for the last decade or so. Especially last year, the returns were crazy. I'm kind of annoyed I didn't make my ISA earlier but it is what it is.
As for ur 2nd Q, the US has literally outperformed every other nation on this planet for years. If you read the FT or Economist, every graph they have has literally showed this trajectory of high US productivity while the EU is lagging behind - though I understand there are other factors besides productivity that contributes to company profits or smth. Thing is, a Global All Cap Index sounds really good as there are a bunch of high potential overseas companies, but I honestly have just started getting into the stock market - practically a newbie, and I have exams to revise for this May so I don't have enough time to go through all these indexes and ETFs. Not sure if I want to stay investing in the S&P 500 for my entire life but it literally is the safest investment so far, in my opinion.