Q1: I create a dkim with port25 wizard but when I show the original message in Gmail I see
DKIM : NEUTRAL ... The setup of DKIM is correct so why Gmail don't know it?

Q2: I have new clean IP and I send 3 emails to Gmail accounts, all this email received in spam folder. Why? I have SPF, DKIm etc..
Even if you have new and apparently clean IPs they may still carry bad reputation from the previous owner. IPs can get delisted from general blacklists like Spamhaus much faster than from ISP internal blacklists. This is where the warm up process comes in - you have to build your reputation.

Email content and spam-trigger words also play a role in why an email can land in spam instead of inbox. You can run some checks with for content related problems. This will also give you a general check on your DNS settings

Also watch your bounces for messages like: Your network is on our blacklist, or Policy-related, or not accepting messages from your IP and then you can get in touch with the ISPs and ask them for a removal, sometimes you can send a message so this is where you tell them you just acquired these IPs new