Don't buy anything. $400 is not a lot of money. You shouldn't be just wasting it on random tools.
That money was hard earned. Put it in the bank and keep it so you can pay your hosting/domains. If you've not already got a vps then invest in 1.
All these tools will do for you is save you a bit of time *IF* you know what you're doing, but you don't know what you're doing when it comes to SEO so there's a 99% chance you'll waste your money buying tools.
Social bookmarking is not going to push you up the ranks by much if at all for anything except micro niches.
You want backlinks from relevant sites in your niche that THEMSELF have good backlinks. Social bookmarking/directory submissions etc have minimal value, they're more of a boost.
Also don't blast a brand new site, build up your backlinks slowly so it looks natural.
If you went out and bought say scrapebox or xrumer then judging by your knowledge you would just go and blast your site with it, which isn't a good idea. You want to setup a linkwheel and blast the parasite hosts as they won't get sandboxed. All that will happen is the backlinks will either count, or they won't count.
Stick to what you're already doing and double your money. You only move on to new projects when you've scaled something as far as you can reasonably scale it. Ie, if you'll need to spend 12 hours a day keeping something scaled then it's probably not worth it and at that point you should try other things, where-as if you can get something scaled up and then maintained with only a couple hours work a day then you might want to think about doing that and *then* moving on to new projects.
But right now, money in bank, get a vps if not already and use money for domains/hosting. Financial security should NOT be overrated. Treat your marketing like a business. No successful businessman will ask the question "right, I've made money what can I spend it on now!" THey understand that having money in the bank prevents you from having a cash-flow problem which can stifle your business and cause tremendous stress.
And forget about this "I want to make $10k next month". If you went to a business advisor and told him you're going to make 20x more profit in 4 weeks he would laugh at you. Even double he would say is unrealistic, but in marketing you *can* make faster money than in most business, but not 20x profit in 4 weeks unless you're already very experienced and just setting up more fast-track campaigns.
Doubling your money each money is the max you should aim for, aim low and you'll feel good when you beat it. Aim high and when you fail you'll feel miserable and demotivated. All this 'aim for the sky' stuff is poppycock. Richard Branson didn't make millions over night. It took him years and years of hard work.
Would have to agree with you on everything EXCEPT two things.
1) Scrapebox - its a steal for $57, but like Hexalor mentioned WAY to many idiots go "omg hai fr33 backlinkz!@@!! lets do a 1k blast!!!" IMHO here is what you should do (and what I do)
a) Web 2.0 (linkwheels) go ahead and blast them. You'll get more link juice, all that really matters.
b) Linking to your main site via manual commenting ONLY Call me paranoid, but I haven't been sandboxed yet, and I'd like to keep it that way. What I'm getting at is ScrapeBox --> High PR, Do follow Blogs ---> Manual Comment(relevent)
I'm not risking being raped by askismet, no thanks.
Thats the only tool I literally think is a MUST HAVE. Yes, SEnuke will help with Web2.0, social book marking etc. But just dish out $4 and get some guy to do manual book marking. Niche Finders, yes they help, but nothing that you can't do manually. Yes, it'll be a pain in the ass, but its not a necessity. And trust me, you'll be in love with web 2.0 after about your twentieth site.
2)
a) VPS, definitely good, but for the time being, a shared account will do. I mean most manages VPS will run you $40. Eventually you'll outgrow your shared acc. but just upgrade it. Unless you got an absolute shit hosting company, most will gladly xfer domains and content to your new VPS for free. Just a little money saver I guess. $6 or whatever versus 30-40.
Just my 2 cents, but yah what hex said is pretty much spot on.
Oh and another thing about tools, is I think its good to gain experience manually before automation.