Your question is more complicated than you think.
Items that increase your Multiplier do so permanently.
The XP Collider has a temporary effect of raising your permanent Multiplier by 5. So if you have a permanent Multiplier of 6, then the XP Collider will multiply that up to 30. Please note that the X5 multiplier does not show up in your Conform-o-meter, just the permanent figure is shown.
You can purchase charges for the XP Collider in units of:
- 24 Hours
- 3 Days
- 7 Days
- 10 Days (best value)
Ok, now for some advice from a long term player (7 years experience and I'm a Hero in the EA Answers forum).
Hold off on spending your donuts until you've gotten all of the first 60 levels of content completed. After level 60 there are no "Level" characters or buildings to buy. They just start giving you donuts for each time you Level Up.
Now start buying Purple, Blue, Pink, White, and Orange houses. They pay for themselves until you have a big bunch, then they increase your income hugely. This is called House Farming. You'll need that cash bump...
Make a space big enough to hold 36 (or however many you feel is the right number for you) Kwik-E-Marts. Do NOT buy them yet, just make a space for them with nothing around that can be sold.
Save up 25 donuts. Easy peasy since you get a donut every time you level up. Once you get to level 939 it changes: you get a donut box for every million XP which can have 1, 2, OR 3 donuts in it (or you can buy 2nd and 3rd chances until you get 3 donuts).
Now charge the XP Collider for 10 days. During those 10 days you'll be buying Kwik-E-Marts, letting them 'build' for 4 hours, tapping them to collect the ENORMOUS amount of XP they produce, then selling them. Doing this will bump you up though the levels like lightning.
So now you're collecting lots of donuts. Start buying Mr. Burns Mystery Boxes from the Premium menu (Homer Budha icon in the store). Each one costs 6 donuts and it cycles through a pattern. This is the absolute cheapest way to increase your Multiplier. After a few months you can have a Multiplier like mine - the highest multiplier I have in my 5 games is over 2,400. I can produce over 100 donuts a day without doing anything else just by logging in every 4 hours and "KEM Farming".
Here's a video of me collecting donuts in one of my games...
