Is it advisable to start this B2C business if you don't have big money for marketing and ads?

Yes, this is a great idea. You don’t need to have money in order to start a business but you need to spend the time to grow your business. Instagram and tiktok are some great places to get your brand out there so you can gain new signups.

I would say this is an ideal is a good start with passion.
However, it doesn't mean it is a good idea.

What triggers you to kicks start doesn't mean you will end up doing the same.

Why do people buy from you? Only if your products solve their problems. Do you think nail designs worth or nail 3D printed is what the customers are buying or buying both?

Selling nail designs can be a tricky one - you are selling designs or selling intellectual properties? The designs can be stolen, while intellectual properties will be harder. So how to build and test the intellectual properties (which can be visible and invisible types)?

Next, how can you ensure the fulfilment of the order? Shouldn't you need to test the process flows and decide on who to partner with to cover the gaps you lack?

The list goes on ... what I like to highlight here is to test an idea, you need to cover the testing holistically so as to ensure your next move from Startup to increase $ and time to grow a business is a smooth sail.

Concept/ idea (make sure you cover all the above) => try evidence-based testing, logic test, stress test, and survey.

This is a good idea, you can definitely start without having to spend so much money on marketing. You have social media which are all free to promote and also there are many other ways to promote for free and also for a cheap price. All you need is a good marketing plan. For further explanation regarding this topic, feel free to ask me any question. use https://clarity.fm/asmahuss/parallel395 link for a free call.

Sorry to break the dream, but creating a marketplace from scratch is expensive, simply because 1. you have to create awareness and design an offering matching 2 different users (vs. one for an e-commerce platform for example) and 2. you can start with only a couple of users, you need to reach a certain scale to see a marketplace alive.
Also, testing the idea (and most probably iterate it) is going to cost some money and/or time.

You do not need a huge amount of money for marketing or generating ads. There’s a bunch of tools you can use that would give you the same results you desire. What you need is to nail your marketing strategy and understand your consumers well on the platforms you will be using for your marketing.

Feel free to call if you have any further questions. I can teach you the different ways you can market while working within your budget or even less!