Hilafat card is not useful for me
Why not? I still think the Hilafat card is your best option. It's very inexpensive and a very efficient and comfortable way to travel between the airport and the city and the city itself. Yes, you have to pay for the card itself but at less than $3USD this still beats pretty much any alternative.
For detailed instructions see: How can I use the public buses in Abu Dhabi from/to the airport and inside the city?
EDIT
There is no day pass but you can preload the card with what you think you need and top if off if you run out. For example you if you buy a card (10 AED) put 20 AED on it, you can ride from/to the airport plus 4 rides inside the city. If you need more rides, just put another 10 AED on the card. If you are planning to ride A LOT, you can get a weekly pass for 30 AED but that doesn't include the airport so you would need a another 8 AED roundtrip for that. Total for that would be 50 AED or less than US$14. Still a great deal, IMO.