My biggest problem was always mining enough hylat for the cannons and sertise for the shields. Both are difficult to come by in early game.
As Edymnion suggests, the cannons are unnecessary. The only reason to marry cannons to salvage beams is so that you can have a single continuous beam salvage array instead of two of them that alternate. The single array with cannon will weigh exactly as much as two salvage arrays without cannons. When using salvage arrays without cannons, you just cycle between them, switching to the one while the other recycles.
For shields, just buy them off of shops. If you are playing in a heavily played out, older universe, you may have to visit a few shop outside of the spawn system, but you should be able to find some for sale. Just sell stuff you've mined for cash, or make a slew of advanced factories and sell those for the cash.
Also with regards to selling stuff for cash with which to buy shields, note that there are some particularly useless things you typically wind up with way too much of; sugil, chabaz, cinnibar, varis, tekt, & lukrah. Usually people have already sold as much of this junk as possible to whatever store you are trying to get cash from. What people usually do 'not' do however is to process those things into their carved brick versions. The carved versions sell for nearly two million for a stack of 50K and most shops are happy to buy a full stack of each.