Could you recommend some advertising platform?

[eucalyptus]

A lot of people have already made some suggestions here. I have experience in e-commerce. I run Google Search Ads and Shopping Ads only. Conversion rate is quite good because our website landing page is quite good also. You can try Bing Ads also. They have different audiences.

But I can also suggest you to create a niche an Instagram and Pinterest page. If you have a budget you, can buy pages that already have followers and in good engagement-rate. Think of it as an investment. If you run these pages properly you can get good feedback. And this is an organic Ad for you.

[natefielding]

Do you know about any other service that provides good traffic with a good conversion rate for a lower price?
Thank you for every tip. 

You should at least include your niche because it may vary in a case to case bases. Those you mentioned were really charging high CPM considering the number of their users where your advertisement(s) will be shown. If you're targeting cryptocurrency, then conzilla, cointraffic, a-ads is a must to try.

Have you tried those social media sites such twitter, reddit and quora?

Reddit is a pretty good one platform when it comes to marketing imo different subreddits will make it much easier

[ei_melai03]

I think you should try craiglist.com. Create your own account and you can advertise your product without any expenses. You may post based on the category of what you are selling. You can also include pictures and text of course. Just make it sure that you are selecting the right category or else your post will be deleted. It is being used here in the Philippines also in other countries. I am using it for 3 years and it's great.
Try also creating google forms if you can so you can have your own website, there is a lot of tutorials in youtube where they can guide you how to create a new one. It wont cost anything, just a little effort will do.