[CAUTION] Most trades require you to have a bit of Monero beforehand for a temporary insurance deposit! (So that no party pussies out after opening a trade or the trade takes too long.)
Quitting a trade midway is very bothersome and Retoswap limits new people with time and mandates completing the trade within 4 days. 4 days is a long time and you will manage!

[CAUTION] Look up holidays in your and their country to avoid disputes later so that there is no 4 days in a row when somebody's bank does not process transfers - depends on your method but still keep it in mind. Past 4 days they can unilaterally just take your deposit (I think).

For a typical insurance deposit (or whatever the appropriate name is) they demand is 15% of the sum you wanna buy. Usually between 10% and 25%. So assuming the most common is 15% - you would have to deposit 0.15 Monero if you want to buy 1.00 and only then pay the full price of that 1.00 Monero. After both sides confirm the trade went good - the insurance deposit is returned to both of you. That is how it is.

So assuming you have no Monero at the moment - this standard is NOT YET unavailable for you. Luckily there is a panel saying "No deposits" where you can find people who list offers for newbs but they are few and expensive. It it is something you need to do once in your lifetime assuming you do not blow it instantly on drugs and gotta buy Monero from 0.00 again XD. I bought just below 0.25 Monero for my first time from some german Julian via Wise with euros (assuming it was not registered on fake documents). Thank you Julian. I paid quickly, 2 minutes and the guy got the money. Once he confirmed everything is ok it took him 2 minutes to send me Monero. Simple.

[NOTE] Do not fear giving your real email and your real life name or whatever else you need to fill up to the dude. It is p2p - they don't care and don't record it the same way you don't care what their name is. If you don't do it properly you might have a hard time proving before mediators that you indeed paid your part if you had any troubles.