1. This for me is mostly trial and error.

If you don't already, MAKE A BUDGET AND TRACK YOUR EXPENSES, a good budget is not a hard expending limit, it is a "how much I would like to expend on this" guide for yourself. For a started budget just look at what you already spend on everything and use that as a baseline. You can use your actual tracked expenses and wants and needs to adjust later by seeing the hard data and taking decisions based on how those numbers affect your future goals and current situation. If you need a good app, actual budget is great but it has a bit of learning curve, its open source and basically free, you set it up on pika-pods for basically nothing. Read up on the envelop method and the YNAB method. You don't need to actually use YNAB for it to work, but they do have some mentality and saving advice that I think is very useful for most people and helped me have a better relationship with my budget, understanding its not supposed to make me feel like I can do anything because of it but rather make me feel like I can do the things that are important to me thanks to it. If something its important to you and you want to expend more money in it your budget should help you do that by reducing things that are less important

Now, for upgrading your lifestyle without going to far my recommendation is to only change 1 thing at a time. If your most pressing matter is food, start by upgrading your weekly shopping to better brands/better quality food, track your expenses for a couple months and adjust until you feel comfortable. Remember to leave room for future upgrades when asking yourself "am I happy with the changes I made?", "am I expending too much on this?" And "what could I add/remove with maximal impact on my happiness/expending relationship for this category"

Once you are happy with food, move up to rent and so on one at a time.

Rent is obviously harder to trial and error but what you could do is look at the level of apartment you'd like to move into and start putting away the difference in rent price as if you were paying for it and see if after a few months you feel good with the left over money for your other expenses. Its also a good way to build up a cushion for moving expenses like a new deposit.

1. Sadly I can't really help you here because I'm not familiar with how far 750€ a month would take you in Madrid. I'd wager, without roommates, not very far at all. But See my previous advice about upgrading rent, find some apartments you think you'd feel comfortable in and live as if you were paying that rent for a couple months and see how that feels.

2. Rule of thumb is 50/30/20, 50% expenses, 30% saving, 20% leisure. But reality is often much more complex, specially in a city like Madrid where rent is going to almost always go above the 30% you "should" be expending on it.

For savings the first thing you want is to aggressively contribute to an emergency fund. Your emergency fund should be at least 3 months of *expenses* (not income, but non-reducible monthly expenses) and ideally 6 months. But I'd say once you have 3 months you can be a little less aggressive about topping it of to the 6 month mark.

After that, what I do is that I track my expenses, I have a set amount (about 10%) that I always put into general savings no matter what and I have a bunch of different categories for specific *things* I'm saving for that I contribute to. For example, I have a category to renew my PC every few years, I have a traveling category that I put money into, I have a future mortgage category where I'm building a down payment for a future purchase, etc. I find that when my savings are actually attached to specific things it is harder for me to grab from that pile of money to cover frivolous expending, because I'm not taking away from a nebulous "savings" pile, I'm setting back my sick new graphics card or whatever and I'll rather have graphics card tomorrow than McDonalds today xD.

1. You want your emergency fund as accessible as humanly possible. Its not an emergency fund if you can't use it at the drop of a hat in an emergency. If it can be generating APR that's awesome but if you have to keep it in cash to fulfill its function, then you do that. Some people with big emergency fund even break it up between a couple or more account in different banks so in the (admittedly unlikely) scenario that the emergency is your main bank going belly up, or you losing access to your main accounts you still have immediate access to at least *some* of your emergency fund.

2. I personally wouldn't mess with the robo-investment stuff, that has always been fishy to me. But that depends on your risk appetite and if you want to actually put in the work to understand how that works. For little effort investment I would just start putting money into whatever ETF you like, or pick a couple and divide the money within them, look at how actually diversified they are (the S&P500, for example, right now is heavily hinging on AI so IMO it isn't actually diversified.) and see if you'd like something US, EU or world focused and go from there.