& deep breath.
Do you have support from friends/relatives who might like to help? Mil insisted on buying cot for dc1 & my parents helped with a travel system. Even if their budgets can't stretch to a big ticket item, they might prefer to contribute towards something you really need rather than a cute outfit.
Nappies, if you're going disposable, buy what you can afford when they're on offer. Same with baby wipes. You'll be amazed how many you go through.
Buy only basic baby clothes to get you started, babies grow so fast and need comfy easy care vests and babygrows (possibly several a day!)
check out your local area to see if there are any nearly new baby gear markets near you. I know you'd prefer to avoid second hand, but no matter what the marketeers say baby doesn't need everything new. I have clothes from dc 3 that still have tags or were only worn once. They'd still be classed as second hand. All of mine have worn hand me downs and used borrowed or second hand equipment, and most people would class us as well off.
Yes to a new mattress (cut cot death risk) but most kit is outgrown so quickly it's barely used. Research new prices for the kind of thing you're after so you know what's a good price.
Alternatively keep an eye out for the supermarket baby events, they often have gems, and remember baby doesn't need everything on day 1, and also that many people get given gifts of clothing/toys after the baby arrives. No matter what the circumstances most people love to buy even something small for a new arrival.
It may not have been your plan to be a mum at this stage in your life, but congratulations and enjoy your new baby cuddles when (s)he arrives.