When you get no response to your offer its probably because the team you're trying to buy from is inactive.
3 or 4 tokens are acceptable for me depending on the player, but buyers have to bear in mind what a similar player would cost (in tokens) from auctions.
A 20 year old player at 99% does not sell on auction for less than 20 tokens in the opening days of a new season.
You're just having bad luck that the players you want seem to be at teams that aren't being managed at the moment. Keep trying though. Good luck.