First issue sounds like you're taking quite a bit of auctions which gives you a lot of debt. Pick and choose selectively which ones you want to take. You can't have all of them. It also sounds like maybe you should let some of the auctions go for low tiles across the map.

Second thing to consider is that scavengers typically don't use iron and steel. There are certain isolated circumstances where you might do it for a period of time but typically you don't claim an iron tile at all as scavenger. If the price of steel is high and iron is low just go into steel for a little while next to your base and then switch out when the market tanks. Otherwise you should be producing other things (because the other 3 HQ's produce steel and you're just selling it off and making it cheaper for them to upgrade by producing/selling steel).

Third is that you need to be very careful about which tiles you claim and how far away from your HQ they are. Fuel costs are doubled in beta 8-9 and so a tile very far from your base might end up costing you more debt. Instead of the high silicon across the map take a low silicon that's closer. You may even find based on the shipping time/distance that you get almost as much silicon from the mine closer to your base.

Fourth - when are you producing power? Scavengers don't normally use a lot of power but if you were producing steel and electrolysis reactors (or glass) you were using a lot. Make sure you've claimed a geo or have a wind farm or solar panel by HQ 2 or 3. Watch the price of power and adjust accordingly. Remember that these power producing tiles are keeping you from going further into debt and not adding to your cash so you don't want to go overboard with them unless you have close to $0 debt and you're trying to make money on power.

Last thing to remember: just because something has the highest price doesn't mean it's the most profitable to produce. A steel mill produces at .5 whereas a low iron mine produces at 1. If the steel is $95 and the iron mine is $50 you're making more money from the iron mine than the steel mill (not even factoring in the power costs which could tip the scale more heavily toward the low iron mine). Electronics typically have the highest price but you only make .25 per tile with those. Just something to consider.

Hope this helps! Also consider watching some videos on youtube to get a good sense of the build order and what people normally do to avoid debt and build a more efficient HQ. Zultar, Cubit, and PBhead have some good videos out there to name a couple. They're 3 of the best players so very good to learn from.