I would focus on one tower at a time whilst maxing up barricades. Unless you are aiming for a higher ranking which imo you don’t need to do until you have started maxing out your towers, so you probably want to focus on levelling up King and winning gems. Having a few higher level towers can help create a base which can generate gems.
I made the mistake of changing all my towers to be skull/fire bolt and at lv 1-3 they are rubbish. Particularly the skull towers. I don’t have max sonic blast or blade storm yet but even so these towers just crumble. so I am slowly trying to upgrade them all. I use my 1 & 3 day gold shields when I get the gems to upgrade 1 or 2 towers in key positions. Its slow progress but a good skull tower on the other side of a path near the beginning of the map can wipe out enemy troops unless they bring cannons. If you have arblasters and gargolyes in defence they can help to stop this.
Another tip is when you cant get enough gold for upgrades or you don’t have workers, keep playing to level up king and then burn money on granny. I have 10 spare slots. If I buy items 1m+ gold value (~10% return on selling) I have 1m gold protected in sellable items. I can do this once every week or so which helps to get higher value towers without using.