Qual é a diferença entre gain e obtain e secure ?Podes indicar apenas respostas exemplo.

All of the words are pretty similar.

Gain means to have it given to you. Although it is usually not used with objects but with other things.
I gained a level in the game!
I gained a lot of experience from this.

Obtain is like if you had to go out and get it yourself. It usually means it was harder to get.
I obtained this piece of jewellery at a vintage market.
Obtaining a large sum of money is not easy, unless you gained an inheritance.

Secure can mean you went to a shop and asked the owner to hold onto it, till you buy it later. It means that it would have gone quickly if you had not acted.
I managed to secure the dress I was wanting!