Yes, you can probably purchase these insignia and boosts for gold, but ideally they have to be used like with 200-300% efficiency, plus proper gold price should be like 30-50% of what is cheapest ratio always available for 100 euro pack (24k gold). And in general don't forget that a lot of this stuff drops from containers for variety of activities (daily logins, SO, contracts), so active players can rightfully say that such items are not worth spending gold at all.
Best use of such stuff is combo of Premium + x2 daily (and x4 SO) + event boost + 2x boost + insignia in case of new player one paid 12h platinum + free 2h which is drop from Silver, Gold, or Platinum chests. Maximum benefit is possible when progressing multiple lines, so boost applies to multiple x2 daily runs bonuses for first victory. Also, in theory if you are playing PvE, you should never enter missions with low base XP gain and/or high risk of failing them.
Bundles are typically high price tag, their content has to be analyzed individually for what they offer. Certain items may obsolete over time and some items are collectibles without good use in game. If you just need premium tank to earn credits, gold option tier 6 MBT prem with good DPM is sufficient. Probably some bundles may tease with different kinds of boosts, so their combo is truly powerful, but i am not sure such are available anymore (like Platinum/Gold AW or Gold Battlefield), I think there is only Platinum Battlefield.