There's no reason to tank. If you end up winning Div 3, you'll get some bonus cash and you can sell tickets at higher prices in Div 2 also. So I wouldn't put any thought into trying to lose games, but it's important to not let winning in the short-term distract you from doing the most important thing, which is training and building financial flexibility. So if you're in Div 3, don't get tempted to waste all the money you've saved on getting players just to make a run at a Div 3 championship. If you're training well you'll easily win the Div 3 championship within a season or two without even wasting money on trying to make it happen and you wouldn't have sacrificed any of your cash in the process.
As for staff, if I were you, the only essential staff member to me right now is the trainer. If you have a doctor or PR manager, fire them now so you only have to pay around 2k per week for the basic level guys. This will help maximise your savings and leave more room to spend on the trainer. If you don't have much money, you'll probably have to start off with a trainer who has a more hefty weekly salary but you can eventually replace that trainer when you've got the money to bid on a trainer which has a much lower weekly salary. As mentioned before, I would highly recommend a level 6 (exceptional) trainer but if you have too much trouble making that happen, get a level 5 (superior) for the time being until you can get a better one.
With your current roster, I would take the youngest guys you currently have who are PF/C position (Jayson Goucher, Zdeněk Hrabáček, Bill Panganiban, Patrick Renteria). A players potential is basically their ceiling in terms of how much overall skills points they can accrue, but that's not a major concern if you just want to train some solid bigs. If you ended up drafting a PF/C which has better potential than Zdeněk Hrabáček (who only has 'star' potential), feel free to swap him out with the new drafted player. Just make sure that if you are training PF/C position that you play these guys 48+ mins each in those positions to maximise your development.
Don't be concerned about what their current skill levels nor supplementary skills right now, consider them a bonus. Your primary focus is ensuring after a couple of seasons that you've trained your bigs to be good at 2 of 3 things - inside scoring, inside defence and rebounding. Within two seasons of consistent training, you'll have some really dependable frontcourt players and a wad of cash to help build the rest of your team. And you can even sell one or two of your bigs to help finance some better guards and then you'll be well on your way to being a quality Div 2 team.
Once you've dropped down to Div 3, be sure to look at the 'economy' section and compare your total player salaries to the player salaries floor. The floor is the minimum amount you must pay in player salaries per week. You want to make sure you are not spending much more than the floor to maximise your savings. You'll already be winning most of your games in Div 3 without trying, so there's no point in spending more on a roster that you won't need.