I've been in a similar situation a couple of years ago when I was 20 and started my studies.
My first way was going to my bank and ask them for opportunities to invest my money. I told them quite the same about my risk-profile and knowledge about stocks and that I don't have the time to really manage my money as you wrote above. They offered me some funds, which promised to raise between 3 and 8% over inflation rate and finally I choose three of them and splitted my money. By the way one was an immo-fund, so for investing in real-estate this might be the best idea for small-budgets.
At least one of my preconditions changed a little after that. I started being interested in the stock marked and economics overall, so I took a few minutes every day to read finance news, when sitting in the subway and took a closer look at some shares. Finally I signed up at an online-broker and started trading on my own with little money. The more knowledge I gained this way, the more I recognized, that the things I was told at the bank were rubbish. They promised me scenarios, which came out to be unrealistic, due to they didn't clearly communicate all the fees, which arise. So it took me nearly two years to "get back at zero".
At the same time investing my money on my own not only helped me increasing my economical knowledge, but I also was clearly more successful than I were with my bank's advices. Of course I made some mistakes too, but that's the way you learn. It's better to make mistakes with small money, than later with bigger money.
Sorry for the long story - I promise now to come to an end ;-)
So you see I was quite in a similar situation and I try to give you the same advice, I would give my 20 year old me, if I had the chance.
1) Make clear what time you can effort to spend in managing your money and especially make clear what amount of time you want to spend! Quantify it, like "2 hours a week".
2) Trading in a quite high frequency, as you described your first trading experience, isn't the only way you can manage your money. Indeed it is even one way which needs lots of time and experience. If you made money with trades over short time at the first time, be clear about, that you were lucky!
3) If you answer 1) similar as I would have done during start of my studies by saying "At maximum 1-3 hours a week" (including reading the finance news in the subway). Then maybe long term investments or ETFs might be an option for you.
4) Take a few hours to find some stocks and ETFs which might be a good investment for you (concerning your risk affinity and your personal preferences, your knowledge about certain industries and - don't know whether this is a deal for you - ethics). If it is a share, take a closer look on the product the company offers and (due to you have some economic background) take a brief look in the yearly/quarterly reportings (don't worry the first time you do that, it might be overwhelming). If you feel comfortable with this investment put it on your list. Choose companies, you still have a good feeling without worrying, when you don't look after the stocks for a week.
ETFs are available for a wide range of indices, regions, industries, …, so it's probable, that you find something that fits to your requirements. They are a cheap alternative to a classical fund (and there are studies, which say, that on average they outperform active managed funds, taking the fees in account). But I don't want to talk you classical funds out, if you already decided to invest in classical funds.
5) Fees are your enemy. Before you start try to figure out whether you want to trade via your bank or you prefer an online broker. Especially take a look on the depot-fees and the trading fees. (also take a look on balance-fees, account-fees, or something named like that, because that's often a hidden depot-fee, linked with a account you have to have parallel to your depot). Obviously try to minimize them, but do this before you start, because a change is always troublesome ;-)
6) It might be obvious, but I'd like to highlight this. Diversify! Take the stocks and ETFs which found their way through 4) on your list. Don't buy all of them at once. Buy some of them and then take a week or two and then proceed. This avoids, that you buy all of them maybe on a local high and is called cost-average-effect.
7) When you invested time in selecting your stocks wisely, you wan't have much to do in the following time. Don't be too fearful. Always keep in mind, that dropping courses are part of the game, so don't worry about a slightly minus. Maybe the most important point is: Make some strict rules, like "My limit is -30%, after dropping more than this value I sell the stock" and be consequent, if one rule is broken. Selling with loss is always hard, but a bad investment isn't getting better, if you stick at it. Usually there is a reason, why the course dropped that much, while others rise. It's a hard to admit an error, but ignoring it costs you money.
Overall your job after selecting your stocks will be keeping an eye on them and finding candidates to replace the ones, which drop out by breaking a rule. Overall that's work, that could be done in less time.
I preferred the way of doing it on my own, due to i was dissatisfied with classical funds. In my opinion it was a good opportunity to do some learning by doing without spending too much time on it, combined with a reasonable financial success so far.
But of course funds, as you mentioned aren't bad at all. There is a reason, why billions of euros/dollars are put into them, so if you don't want to invest even a little time (which is ok anyway) they might be the way to go for you. I just didn't want to give advice in this direction, because I chose another way, and there definitely are other people here, who can give you a better advice concerning funds.
Maybe one last advice: Don't give too much about advices from other people. ;-) But you seem to be smart, so I think you'll manage it!
So finally I recognize, that my post got longer than expected, but I hope I could help you.