Best way to spend sugar lumps?

[Ryoga]

Is the garden really worth it??

I have 1 on the temple, 1 on wizards and lvl 3 garden

[Schrute_Farms_B&B]

- 4x sugar lumps to unlock the minigames (Wizard->Temple-Garden->Bank (most important)

And everything else is completely up to you and how you want to play this game.
Personally, I think the garden is one of the most important aspects in the game in many ways. (Take a look here[cookieclicker.fandom.com] Could be overwhelming first, but youll get used to it.
It can practically provide for everything, like sugar lumps or CPS boost, Golden cookie frequency, etc. Really worth to take a look at. :)
The more sugar lumps you spend, the bigger your garden gets to a max of 6x6. A level 3-4 garden is more than enough to start grinding seeds.

The Sugar Frenzy is always worth a sugar lump, to boost a combo (but only if its a rare one like 2x buildings buffs +x7 + x777 + golden switch + sugar frenzy + shimmering veil + loan + etc.

Speaking of which, the loan is optional, too. You could upgrade your cursors to Lvl 2 (3 sugar lumps) to get the first loan stage for your Bank but I dont recommend that, because the penalty time doesnt run out, when you close the game. And it's only a +50% boost so who cares.

Most people spend their sugar lumps on leveling buildings for achievements, which is understandable but you want to do that at the very end.
Each sugar lump, gives you a CPS boost and thats the reason, why you want to stack them until youre good to go.

edit: Happy baking and enjoy yourself.