I dont understand the question. You buy as much as you need! Whatever satisfies your hunger.
What would be a good start?
you need enough fruit to make monomeals. What are your favorites? Personally, when I go to the grocery store I buy 30-40 bananas so that I have them for a week or two. I also buy medjool dates to snack on, a bunch of citrus fruits, watermelons for breakfast, and whatever else looks nice and ripe. Get romaine lettuce and spinach, and whatever vegetables you like. This is super important!
I also buy rice and sweet potatoes for my cooked dinners, and coconut sugar to add to sour fruits. I don't know if you want to be raw till 4 or completely raw but this should be a good start. make sure you have enough because you want to make sure you get at least 3000 calories per day.
Be creative and good luck!
Buying bulk will usually get you at least a 10% discount. Speak with produce managers until you find one you like who's willing to work with you. Start with a full case of nans (40#) and if you plan to incorporate cooked items, get a case/giant sack of potatoes and/or a giant bag of rice. Tender leafy lettuce type greens are essential too, and I personally like green smoothies, so I also get bulk grapes and lettuce as well.
Organic is ideal, but if finances are an issue then conventional is fine. Supplement from there with fruits and veg that looks interesting, seeking to try something new regularly to gain experience and expand your veg palate.
+1 for trying new stuff. Some things are not popular for a reason, but I have no idea why all Americans don't eat fresh gooey dates or soft squishy persimmons as a regular part of their diet. I grew up with apples. To me, apples are only useful in pies haha. Maybe for an occasional cider ;)
and for throwing at doctors to keep them away ;)
Start backwards. Adult females need a minimum of 2,500 calories a day and adult males need at least 3,000 calories a day of fruit. You also need to drink 3 or 4 liters of water a day. So you're going to need enough food to cover that amount of calories, plus some water bottles to make sure you're drinking enough water daily.
If you are new at this, your first task is going to be expanding your stomach. You will be eating a LOT of food every day, and it will be uncomfortable for the first few weeks, until your stomach expands. Easiest way to get the party started is to buy a box of bananas. If you want to jump in fully raw, I recommend fasting the day before and then going on something easy like banana island - eat nothing but bananas for a few days to get your system kick-started. I ate a bunch of regular food the night before I started and boy was that not fun - cooked food is slow-moving and you can get bad gas & pain if you suddenly drink a high-fiber 10-banana smoothie!
I don't recommend things like apples or grapes since you have to eat a ridiculous quantity to get your caloric needs in. Bananas are easy & cheap. Dates are great, but can be hard to find (I now order 100% of my dates online). Mangos are good, but they are out of season right now (at least my area). Oranges are great, but if you're going to drink them, blend the whole orange (minus the skin), don't just juice them & leave out all of the fiber! But yeah, bananas are easy to start out with. If you want to start small, just blend up 4 or 5 of them for breakfast every morning to begin with. Big key is not to eat large quantities of fruit after cooked meals (or even uncooked veggie meals) since your stomach won't feel good; eat it before regular meals if you're doing say Raw Til 4.