If you are independent, this next step is absolutely vital as it will increase your relative strength as the AI perceives it making you less likely to be the next target in favor of weaker ones. And that step is, quite simply, revoke every single county and barony in your demesne until you own them all. But we are not simply revoking, you do this via imprison/banish which will give you not only all of their holdings but all of their starting cash as well, which you desperately need. You may have to do this anyway if you are within the de jure territory of an existing lord as most of them will not have the CA necessary to revoke. But regardless of whether you can revoke or not you do imprison/banish because this will give you their territory as well as their small starting cash on day 1 which is our goal as the AI scans its neighbors for weakness.
Note that there is a piety cost associated with imprisoning and banishing, both are 10 piety apiece and executing is 20 (so if you have any baron or count vassals you may just want to wait for them to die in prison). You may simply revoke (if this is an option) baronies and there is little chance that they will rebel. You lose out on the small amount of starting cash they get but on the other hand you don't have to wait sometimes a couple years for another 20 piety. Do this AFTER any count-level vassals are imprisoned so that you don't take the chance of them rebelling for the imprison attempt. For a quick early boost in piety you can use the papal letter, it's income-based and, as yours is horrible, it will be an extremely cheap 25 piety (1.06 gold in the Iceland test I just did). With that and your starting piety, you should have enough for 2 imprison/banishes, the rest - if there are any - will need to be plain old revokes. Note that this may make Day 1 more like Day 9, but the general concepts remain the same.
Use your marshal (hopefully you got a halfway decent one) to Suppress Revolts on the county of your target and begin your reign of tyranny. Strip counties/baronies/everything - if you are a single-county count then this will be pretty quick. If not then to switch your marshal to the next county just assign marshal to someone else then back to your best guy (who you should revoke last if he's landed!). This will make them hate you but they're going to anyway before we're done. Remember your initial counts/barons may simply require an execute so you inherit rather than banish which is better so there aren't a lot of claims floating around.