Finding durva is not tough. It is short grass with only 3,5 or 7 ends. so it's not tough finding it. you can grow it in flower pot in balcony or terrace. Also if you're placing Ganesha at home for regular pooja try to get durva and grow for self. so that it's clean and pure every day. But there are thing you should know.
FIRSTLY, you need to make a few observations. There are two types of Ganesha statues:
1. Lord Ganesha trunk to the left side – for the home purpose, left-sided Ganesha statue at home should be kept. Because according to books and people Left-sided Ganesha statue is believed to be representing Ida Nadi which is a more cooling side. Also, you can relate it to the moon. It is more feminine, cooling, nourishing and circulates relaxing energy.
It should be remembered that the Ganesha statue should be in sitting position in-home (you don't want your gods standing). Whereas for pandals (During Ganesha Chaturthi festival), it could be standing position or any position.
2. Lord Ganesha trunk on the right side – This is normally the case with Ganesha statues in temples. Also, this statue needs lots of care and rituals. (ALOT more than you're thinking). The same statue resides in the Siddhi Vinayaka temple.
3. Lord Ganesha trunk is facing straight forward – this kind of idol statue is very special.
Also, remember in mind that Ganesha is a sattvic deity. So avoid having non-veg food at home. No onions and garlic should be used in prasad meant for the lord.
Now let's talk about the other idols. make sure to keep Ganesh-Laxmi for home. But if you wanna keep Riddhi-Siddhi, it will ask more care.