Do some research and some math.
Find out how much 2.0 ships will cost, then find out how much that ship costs with or without upgrades. If you buy it with upgrades, you can use it now. Without, you're limited but you'll make the most of your money later.
Then consider some price per upgrade numbers. For example, if you buy one A-Wing for $15, then a conversion kit for $50, you've paid $65 for one ship. Conversely you could just buy the 2.0 A-Wing for $20. If you buy 10 ships at $15 + conversion kit it comes to $200. Buying those same 10 ships for $20 each comes to $200.
There are other things to consider with this, like the newer ships looking nicer than the older ships. Also, the conversion kits will have a ton of upgrades and a wider variety of pilots available that the rereleased ships will not. Another factor is we are only discussing buying one conversion kit here. If you buy 5 Imperial and 5 Rebel 2.0 ships you are paying $200 for the new ships but $250 if you get the conversion kits. Another thing to consider is that you may have time to gather these ships before buying the converters.
If it were me, I'd find out how much I could spend, and if it's $300 or more I'd buy old ships super cheap online and buy the conversion kits for $40 online.