It is preferable to only purchase Mechs at 5-10 dollars when they are not inventory Mechs. If they are legendary Mechs, the right price for them is around 10-20 dollars but no more. When it comes to weapons, legendary weapons with high energy cap like 12 energy or above are your only focus to purchase. The price estimated should be around 1-10 dollars per weapon. It won't matter if they are on low stars if you are willing to grind for their level and you must take in consideration 2 different advises:
1. If you ever see any higher prices than what I have mentioned or rarity other than what I have mentioned they are baiting offers since they are not worth or can be achieved for free or they are given false pricing. Yes, they do give fake prices to scam premium newbies.
2. Pay cheap, grind more. That is how I do it. My recommendation that you should select your end game Mechs and end game weapons from now. Any waste on acoins budget will reflect on you damage when matchmaking system of matches will bring insane bots that are more expensive than whales with their equipment and pilots.