Since the extract equipment can also be used for all grain, I'd just buy a larger kettle that is suitable for all grain (10 gallon+). This way nothing goes to waste, and you can get a little experience with brewing extract before jumping into all grain. When you are ready for AG, buy or build a 10 gallon mash tun and you're pretty much good to go. I personally do not use a hot liquor tank, so I'd say this is not required.
I recently started AG and am no expert, but at a high level, the general steps for mashing are not that complicated but you do need to be mindful of temperatures and water volume. I am not yet experienced enough to make my own recipes so I buy recipe kits. I am now prepping for a brew day next weekend and am going to do water adjustments for the first time, in hopes of improving the beer. Good luck
I recently started AG and am no expert, but at a high level, the general steps for mashing are not that complicated but you do need to be mindful of temperatures and water volume. I am not yet experienced enough to make my own recipes so I buy recipe kits. I am now prepping for a brew day next weekend and am going to do water adjustments for the first time, in hopes of improving the beer. Good luck