Best Build for start?

Best class and build for easy start destruction to get first set and sacred unique for person like me who dont have any.

It depends from which place your hands are growing.

And set items already drop in terror.

Or meyby like that: Bow druid or caster sin generally better and safer?

there is no "best" of "better" . it's all about what you can do/what suits you . someone can say "x" build is the best , but maby you won't make it past mid destruction with it if it's not suited for your playstyle .

make tests , don't let others tell you what's best because their "best" may not always be se good for you.

For druid safest choice is traprat.
As for assassin - haven't played it much in new patch, but it used to be squishy class which gets better in end game with max block and high avoid. So it might be struggle at first.

I started with a bowazon and I'm progressing without much effort, now entering A2 destruction and I already had some Sets/SUs drop, although nothing useful.

From my experience as a total beginner the pros and cons are as follows:

+ Easy LC1, Ennead and LC2
+ Good clearspeed in crowded areas
+ Main weapon can be obtained from tristram giftbox
+ Actually pretty safe farming since you can kill enemies offscreen and stack some mf beause you dont need defense, only res

- really squishy, opening a door without caution can lead to swift deaths

So yeah, I can only recommend doing a bowazon as first char and use the guide in the guide center from suchbalance

Trap rat- tanky, good damage, boring to play.
Totem nec- many meatshields, insane damage, awful gameplay (might be ok if you play it for first time though)
Unholy caster- quite tanky for caster type of class, nice damage, sacred armor. Early-mid game are quite annoying though.
Summon barb- tanky, many meatshields, stomps early-mid game, completely useless in endgame ubers.
Limpet assassin- range, good damage, limpet mechanic is amazing for many ubers. Cancer early game, playing glasscannons is majestic overall.
Caster druid- insane damage, immunity breaking spell, healing spell, meatshield. Awful pre 90 and before moment you get black road challenge skill.
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Cold/lightning sorc- was op for last 3-4 years, got nerfed this patch, so not sure about her anymore.

How mutch hp give skill godberry on like 10 lvl? If 1 givee 2000 how muth more per skill lvl?

I agree with Chuck, each class got different build and playstyle, so you may choose a class you like and readjust while playng. Belladonna's are ezly found in cows