I’d go all out and buy something very nice and of good quality. Don’t focus on the money, just choose something tasteful from a higher end brand. I.e., for a baby shower I’d get an outfit from Purebaby or Country Road. If you have the money and can afford it, it’s better to err on the side of caution and buy something a bit more rather than a bit less. After a little while you will see what everyone else tends to buy and will be able to set a budget accordingly.

I have grown up in a family like this and this is a budget I follow.

Christmas is $50 per child $100 per Adult
Wedding distant relative or co-worker$75-$100, friend or relative, $100-$125, a closer relative, up to $150.
Mother’s Day and Father’s Day $60-$100
Christenings ect $50 unless you are God parent then between $100-$150
birthdays, $20-$25 for a co-worker or acquaintance, $50 for a close friend, or $100 for a best friend or family member.
Bridal shower ect, Regular friends, co-workers, or distant family members $75,Close friends or family members $75 $150

Why is it your job to buy your husband's family gifts? Surely it's his job... Do you expect him to buy gifts for your family?

That’s a cop out hubby has to step up just a little bit. I too come from a similar wog background where gifts are usually more expensive etc and I do all the gift buying it’s seen as the females job. I can still however ask him what he thinks or to give me a ball mark $ amount if it relates to his friends or family members. Your hubby has been babied long enough and should have the balls to ask his mum for some help once a twice or his sisters. How hard is it to say hey mum or sister how much are you giving this person for their wedding. At least once so from then on you have an idea. From the sounds of it your not from the culture as them so it’s the least he can do for you as you are embracing their culture and wanting to do right by them

Some European families can be a bit showy, just bear that in mind.

You are married now but what did you do before when you guys were dating engaged etc what did his family give you for Xmas or birthdays that should give you a rough idea on how much they spend on things. You don’t have to discuss exact amounts but I find it a bit disrespectful that you’ve approached them for help on this as a newbie to the family and they have shut you down completely.

Have you considered a sideways step in the gift giving process and gifting a heartfelt gift instead? I mean, rather than say, a diamond tennis bracelet, maybe a photo keyring of the person (whether with you or as part of a family shot)? Something that money can't buy.
Your husband really should be the one to handle this, or at least help you until you get the hang of it (I know how stubborn wog boys can be - "iTs YoUr JoB tO dO tHe ShOpPiNg iTs A wOmAnS jOb!"). He's known these people all his life, he can hold your hand and advise you whether X is appropriate.

Or deliberately give simple unassuming gifts and make it an endearing trait. ie "why did she give his mother in law a coffee mug" - teehee woopsie doo who else but Quagmire (but with your name)

Write down in a little book what you receive for engagement wedding births christenings etc and you will see how much each person spends. I usually give back the same amount or there abouts, sometimes it changes as sometimes that person might not get married or have kids for yrs and you may not be as close anymore so adjust accordingly.

I don't have much experience (none) with wealthy Greek or Italian families, but would buying an experience be better than an actual gift? Like a weekend away, or wine tour? Teenage scuba/snorkeling session at your closest seaworld type place? Zoo pass for kids? Pamper spa day?
You could spend the money so it wouldn't look cheap but you could also very thoughtfully choose an experience relevant to the interests of the person you're buying for?

Glad my extended family is not stuck up
We are happy with $5 candle and box of roses choc for example

Thoughtful gifts are the most expensive in that it takes your time and effort to find. Money is nothing I wouldn’t be looking what costs the most but what means the most to that person- unless of course you are buying for a teenager.

I find the more wealthy people are, the stingier they are on gifts. You'll just have to feel out what kind of people they are.

We're not really wealthy or anything, but I generally allow $50 per adult and about $20-30 per child (we only have 2 nieces, and only buy gifts for our parents and my brother in law and his wife for Christmas). However if I find something that I know they will love and it's more than I'll still buy it (within reason), and sometimes things are cheaper. So really it's more about finding something I know they will use/treasure than how much I spend.

How about when these occasions arise. You and hubby go shopping together, since it’s his family he will have an idea of gift suggestions and appropriate amount to spend. Once you do this a few times you’ll get the hang of it and won’t need “guidance” anymore.
I’d like to know why money is not to be spoken of? Is this money/wealth a result of criminal activities. Have you just married into the mafia? All seems a bit suss to me 🤷🏻‍♀️

Perhaps a conversation to have with your mother in law as a way to get closer to her also? What nationality are the family? How wealthy?

Ask hubby

The previous reply is very good advise. Try to work out what sort of presents these people will really appreciate, and don't get involved in buying expensive gifts if they are not going to be treasured. Sometimes, people are happier to receive something that you have made yourself, maybe homemade jam or chutney, or arts and crafts if that is your scene. If they are so well off, they probably don't need any more unwanted stuff that just gathers dust. Don't be frightened to ask the family. They would prefer to receive something they like, than something that is going to make them feel like you just bought a gift because you had plenty of money.