Money seems a concern to you, so I am not going to say yay, or nay on whether you should book a throw away room, but I'll give you advice on how to deal with the crowds.
- Get there a little prior to opening.
IoA - That way once they open you're ready to go through the gate at IoA when it opens, as HE can sometimes have a delay at opening.
Universal - You can get through the gate and if you don't have EE you at least wait in the Hollywood area and once the park opens you're already physically in the park.
- Use single rider lines if you want.
Not all rides have it, but a decent amount has SR lines. It will save you a lot of time. Even in times I have EP I will sometimes do the SR line since it's the shortest walk. If you're planning on doing RRR, or Gringott's, do SR lines as soon as possible, as sometimes these SR queues can get long, or open and close later in the day. For WWoHP rides, FJ and Gringott's have SR lines (technically Hagrid does too, but the status of the SR line is unknown to predict in April), but you want to do the regular queue at least once to take in the whole experience, especially if you're a massive fan, so if you want to do the whole queue, but not wait that long, wait for lower wait times to do it.
- If something has an insane wait time wait until near closing hours.
While I wouldn't recommend this for Hagrid's now (however things might change for Hagrid since you're not going until April). Typically for incredibly popular rides with long wait times that never seem to go down, I like to wait until it's late at night, when a lot of guests have left the park and/or when guests are typically watching the night time shows that the parks are offering. It is around this time that typically it's near closing and prior that officially happens you can hop on the ride.
That being said you should be able to do everything you want to do if you're doing two days and wanting to focus on HP anyway.