>A new IG player looking for advice
I have waited long for this day.
The first thing to figure out for yourself is what you want out of this army. Do you want to win, do you want an army that looks cool and abides by a certain theme, or some balance of both? This determines what you buy and field.
If you want an efficient, competitive army:
In the current edition, infantry spam is very efficient and this makes IG quite good now. The price of a guardsman dropped form 5 points to 4, and a conscript is only 3. This and flak armor saves actually are a thing now,since AP only lowers saves, not eliminate them.
On the flip side, tanks are less good than they used to be. The leman russ and chimera in particular are basically just rolling bricks now, able to take damage but not deal it. IG also benefit from a lot of special weapon dense deep striking units like scions and command squads, and now special weapon teams and veterans can share transports and get even more high AP stuff in one box. Artillerywise, the basilisk and manticore both are very good now, the mortar tanks less so.
As for minis, there's pig iron, wargames exclusive, anvil industries and victoria off the top of my head. Also consider the old cadian, steel legion, vostroyan, or even chaos cultist minis as substitutes for the goofy cadian plastics and their earmuff helmets.
Whatever you do, I advise you to take your time to make a converted, interesting mix of units with their own unique look unless you truly are in love with some default color scheme you see in the books. If you try to paint your stuff exactly as you see it in the codex, you will realize on day years from now you spent hundreds of dollars making someone else's army. Never buy a model you think is ugly just because it has good rules - if you really want it, convert it from something else.
You are going to want a lot more infantry - probably at least 150 models, and maybe some tauroxen.