Main thing to buy right now is the bike. Saddle and changing other parts will only be found by riding the thing and can be done in easy stages. I have even known stock saddles to be comfy after the settling in period so I would even stay with that. Tyres and wear out the ones that come with the bike unless they do not suit your style.

What you do need though is the Puncture repair kit in a wedge under the saddle two levers- repair kit and a spare tube is all you need to carry but one extra tube can also be a blessing. Pump and a good one that fits the frame and works. Cheap ones of unknown name do not. Water bottle and carrier and that is about it.

That is all I carry on most of my rides but I also have the capability of extra water in a camelback for the longer rides. (Two bottles and carriers also work) Clothing and helmet is a must. Gloves and Cycling glasses help aswell. Shorts and jersey could come later but most of us want those on any ride of length.

Most people around are looking to save money. Even my LBS knows this and I give them the chance to match the price I can get elsewhere. Most of the time they can and will or at least get somewhere near it. There is an advantage of buying from your LBS but if you can save plenty by shopping elsewhere then at least least you have given the shop the chance to make a sale.