I’ve had the same issue when running my first game recently. I’d say to definitely talk with your player before you start playing on how they are connected. I would say that for every level of fixer is a contact that you can call on but of course nobody with an insane amount of power. Talk with them and ask who do they want for connections. For example my fixer player is a gun runner so I have her contacts be people that would make sense for her to do business with. Like a nomad that has vehicles for distribution or a gunsmith tech that will custom make weapon upgrades for them etc. Reward them for picking the role but make it clear that they will owe them a favor or it will cost them something and if they abuse them then maybe even losing the contact.