Hi Natalia ,
I guess I can't be really helpful as I can't tell you 'buy this one' , it is a big pressure and a matter of taste . I can say for sure I like a lot your look from the virtual-wig picture .
I don't know , if you go in the store you really should ask them for all kind of advice and also try many of them and see which one make you look the way you want . I know I sound so fake , and I guess I am , after all if it was me I would chicken out so bad

But you should do it and maybe you should go as 'you' and not as a 'boy' , show your femininity in style / voice / looks and I guess it would be easier and more natural to express your need and be understood . I can't think at a 'silly lie' that would make sense or - even more important - be helpful for you .
I am really no expert , but I know you have to style them. Again , the store should give you more advice .
My 'style' is to buy things online when I am ashamed to go in the real store , but I don't recommend that , I feel like I am wasting my life this way . You could ask them online for more advice in styling it / maintenance and other stuff you are interested in .
Anyway , I wish you good luck and have fun at shopping . You won't need the wig for long anyway , your hair is beautiful and it will grow in length and volume in no time

I wish you a great day ,
Claudia