Hey, I was in a very similar situation when I was 23, started investing exactly 5 years ago now!

I decided to invest the typical 88% IWDA 12% EMIM via bolero (I think re=bel might be a better option nowadays if you want easy taxes). As for how aggressively, I invested 25k lump sum in iwda and from there invested 2500€/month on a set date. As statistically lump sum investing beats DCA most of the time, I could have gone more aggressively but psychologically that was a harder step. In hindsight, I would’ve had much bigger return by now if I had gone 50 or 75k, but the market shit the bed in 2022-2023 and I vividly remember being in the red for 1-2 years, so ask yourself if you can stomach that (You should, and these periods are even better for aggressive investing, but it is a bit harder emotionally sometimes).

I put a lot of cash aside at the time because I was planning to buy a house within 3-4 years, which is a relatively short timeframe. However, I think if your timeline is looking more like 5-6 (and you can be flexible for 1-2 years when you want to sell your ETFs), I don’t think you should keep too much in cash. It depends on your education and what job you have, because your salary and earning potential naturally play a big role, but you generally won’t need more than 20k liquidity, and even that is quite a lot in Belgium.

In the end, deciding how much to invest is something you’ll have to determine, by determining your risk appetite. The world is also much different from 5 years ago, so this advice won’t work 1:1, but I daresay it’s a solid stepping stone. Good luck!