Budget is definitely important for a successful business, but it is not everything! As a young entrepreneur, I started a similar business earlier in my career selling eyeglasses on eBay. I created an eBay store, worked on advertising, and was fortunate with my results. I would love to speak with you about starting a website and marketing effectively to consumers with a very small budget. The biggest recommendation I can provide is to test different services at a low budget to see what works. Rather than spending thousands of dollars on a marketing agency, there are many services that can help your iPhone case business in marketing effectively. Feel free to reach out to me!

First lesson, validate your market first. Start with small experiments in selling and marketing before you take on bigger deals. Start with first base before you try for a home run. There is no magic answer - if there were, there would be tons of very rich people which may not make sense. Start doing smart experiments - research, go to conventions, get online, interview people in different markets, look at the trending stats on google and youtube.

Budget is important but not a 100% essential ingredient for a startup. You should consider employing some of the lean methodologies if you want to optimize on the budget you have .
Startups which deal with information management typically require intellectual capability more than financial muscle. So you can consider starting an internet related startup.
Similarly selling on-line helps you to minimize the marketing costs as you can reach out to initial critical mass using various social media channels/forums to get going.

I would love to have a call with detailed guidance on each of the sub-questions.

You may want to consider a dropship business where you don't need to buy inventory at all and have suppliers shipping directly to your end customer.

Before you spend any money on inventory, survey your target market and build up demand. Be creative in designing an engaging campaign that allows you to "presell" purchase orders (simply taking a poll on who actually would be a paying customer). Give these individuals a discount, which in terms of your cost basis is simply the price of the risk reduction when you go and make your first inventory purchase.

Once you've acquired enough demand, negotiate your purchase price with the suppliers and arbitrate the sales with those who expressed interest.

You'll be cutting into your margin, but you will be reducing your capital risk, and "bootstrapping" your market demand + cashflow for future runs.

Have you spent any time to learn about coywriting? My best guess is that leaning some basic copywriting techniques will help you to sell whatever you eventually decide to start selling.

Whatever you do, first ask yourself "what are my strengths". Do not just follow some friends which do good money on this or that. Everybody has his / her own strengths and talents.
If it is ok with trade, then you have to do marketing research:
- which product
- target group
- market price
- production cost
Do this for all products you have in mind. It is difficult but worth.
The difference between the market price and production cost will tell you whether to go or shift to another.
all the best
Val